2. First, bacteria, good or bad, are spread around the globe because people travel and goods are traded from one place to another. Key: the __________ of bacteria （some beneficial and some harmful)

A、Right

B、Wrong

C、Not mentioned

D、----

__ "

A．killing the bacteria in your body

B．multiplying to a significantly large number

C．raising the room temperature

D．sterilizing the perishable food

A．By controlling the temperature

B．By putting food in a refrigerator

C．By controlling the growth of bacteria

D．By putting food in a place without air

How does the professor help the students to remember the types of bacteria？

A．He shows them many examples of slides.

B．He tells them to look at specimens in the lab.

C．He uses the first letter to represent the shape.

D．He explains the various DNA structures.

A、A. Diseases

B、B. Cells

C、C. Bacteria

D、D. Invaders

NASA Inventions You Might Use Every Day

In 1958, President Eisenhower signed the Space Act, officially creating the National Aeronautics and Space Administration. From the beginning, the purpose for the new branch extended beyond space ships and moon boots. The law prescribed that its research and advancements should benefit all people, and in its 50-year history, NASA has certainly fulfilled that role.

Although most people today will never set foot on the moon, everyone likely comes in con tact with a NASA by-product every day. Partnering with various research teams and companies, NASA continues to produce a vast array of new technologies and products that have improved our daily lives. Basic steps in health, safety, communications and even casual entertainment find their roots in the government branch commonly associated with rocket ships and floating people. In fact, NASA has filed more than 6,300 patents with the U.S. government.

Each year since 1976, NASA has published a list of every commercialized technology and product linked to its research. The NASA journal Spinoff highlights these products, which have included things like improved pacemakers, state of the art exercise machines and satellite radio. Each product was made possible thanks to a NASA idea or innovation.

But it doesn't take a rocket scientist to use many of these so-called by-products. Read on to learn about some of these familiar products.

1. Water Filters

Water is the essential ingredient to human survival. Since people cannot live without water, the ability to convert contaminated water to pure water is an incredibly important scientific achievement.

Astronauts needed a way to cleanse water they take up into space, since bacteria and sickness would be highly problematic. Water filter technology had existed since the early 1950s, but NASA wanted to know how to clean water in more extreme situations and keep it clean for longer periods of time.

If you look at a water filter, you can usually detect small chunks of charcoal (木炭) inside of them. Sometimes, when you first use a water filter, you'll even notice tiny black flecks from those chunks. This charcoal is specially activated and contains silver ions that neutralize bacteria in the water. Along with killing bacteria in the water, the filters also prevent further bacterial growth. Companies have borrowed from this same technology to bring us the water filter systems millions of people use at home every day.

2. Cordless Tools

When you're sucking up bits of dirt or crumbs around the house with a handheld cordless vacuum, you are actually using the same technology that astronauts used on the moon. Although Black & Decker had already invented the first battery-powered tools in 1961, the NASA-related research helped refine the technology that led to lightweight, cordless medical instruments, hand held vacuum cleaners and other tools.

In the mid-1960s, to prepare for the Apollo missions to the moon, NASA needed a tool that astronauts could use to obtain samples of rocks and soil. The drill had to be lightweight, compact and powerful enough to dig deep into the surface of the moon. Since rigging up a cord to a drill in outer space would be a difficult feat, NASA and Black & Decker invented a battery-powered, magnet-motor drill. Working in the context of a limited space environment, Black & Decker developed a computer program for the tool that reduced the amount of power expended during use to maximize battery life.

After the NASA project, Black & Decker applied the same principles to make other lightweight, battery-powered tools for everyday consumers.

3. Long-distance Telecommunications

The ability to carry on long-distance telephone conversations did not happen overnight. It doesn't

A．space travel

B．national security

C．people's welfare

D．economic development

he most ancient living things, which exist on this planet for nearly 4,000 million years. Do you know the size of bacteria？ It can only be measured in microns. Maybe you have not a standard in your mind how long a micron is. One micron is a thousandth of a millimeter, which equals about the diameter of a pinhead. Therefore, even if we enlarged the rounded bacterium a thousand times, it would only be the size of a pinhead. We barely see bacteria by a magnification an ordinary microscope of 100 times, even if we try, we cannot make out anything of their structure. There are normally millions of them together, for they can multiply really fast.

Scientists have found that some bacteria have attached to wavy-looking "hairs" called flagella. The flagella rotate, pushing the bacteria through the water. Others can glide along over surfaces by some little-understood mechanism. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. They are active all the time. Even the bacteria without flagella often bound about in the water. They are pushed here and there, colliding with the watery molecules.

Bacteria cannot be detected because they don't produce bad odor or change the color or texture of the food. Therefore, when people eat the food with many bacteria, they are likely to get hepatitis A, acute gastroenteritis and a host of other illnesses. Many households have refrigerators to prevent from bacteria. Of course, freezing food slows or stops the growth of bacteria, however, when food is thawed, the bacteria will become reactivated. Bacteria can not be totally destroyed before the food is thoroughly cooked. We need to know that not all bacteria are in connection with illness. Just some bacteria can cause disease. They are called pathogenic bacteria. Fortunately our immune system can protect us from them.

Bacteria are prokaryotes (single cells that do not contain a nucleus). It may seem weird to classify organisms according to such details, but with or without a nucleus is not trivial at all. The division between prokaryotes and eukaryotes (all organisms with a nucleus inside their cells) is of extreme importance in biology, and is the result of a major evolutionary breakthrough. Visit our program tomorrow if you want to know more, thank you.

Which of the following is true according to the first paragraph？

A．Bacteria are as big as a pinhead.

B．Bacteria can not be seen by an ordinary microscope.

C．Bacteria are hard to see because they often live together.

D．Bacteria are very small so they can only be measured in microns.

Text 2

Bacteria are microscopic organisms which live on the surface of objects. They are one of the most ancient living things,which exist on this planet for nearly 4,000 million years. Do you know the size of bacteria？ It can only be measured in microns. Maybe you have not a standard in your mind how long a micron is. One micron is a thousandth of a millimeter, which equals about the diameter of a pinhead. Therefore, even if we enlarged the rounded bacter:ium a thousand times, it would only be the size of a pinhead. We barely see bacteria by a magnification an ordinary microscope of 100 times, even if we try, we cannot make out anything of their structure. There are normally millions of them together, for they can multiply really fast.

Scientists have found that some bacteria have attached to wavy-looking "hairs" called flagella.The flagella rotate, pushing the bacteria through the water. Others can glide along over surfaces by some little-understood mechanism. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. They are active all the time. Even the bacteria without flagella often bound about in the water. They are pushed here and there, colliding with the watery molecules.

Bacteria cannot be detected because they don't produce bad odor or change the color or texture of the food. Therefore, when people eat the food with many bacteria, they are likely to get hepatitis A, acute gastroenteritis and a host of other illnesses. Many households have refrigerators to prevent from bacteria. Of course, freezing food slows or stops the growth of bacteria, however, when food is thawed, the bacteria will become reactivated. Bacteria can not be totally destroyed before the food is thoroughly cooked. We need to know that not all bacteria are in connection with illness.Just some bacteria can cause disease. They are called pathogenic bacteria. Fortunately our immune system can protect us from them.

Bacteria are prokaryotes (single cells that do not contain a nucleus). It may seem weird to classify organisms according to such details, but with or without a nucleus is not trivial at all. The division between prokaryotes and eukaryotes (all organisms with a nucleus inside their cells) is of extreme importance in biology, and is the result of a major evolutionary breakthrough. Visit our program tomorrow if you want to know more, thank you.

46. Which of the following is true according to the first paragraph？

[A] Bacteria are as big as a pinhead.

[B] Bacteria can not be seen by an ordinary microscope.

[C] Bacteria are hard to see because they often live together.

[ D] Bacteria are very small so they can only be measured in microns.

he most ancient living things, which exist on this planet for nearly 4, 000 million years. Do you know the size of bacteria？ It can only be measured in microns. Maybe you have not a standard in your mind how long a micron is. One micron is a thousandth of a millimeter, which equals about the diameter of a pinhead. Therefore, even if we enlarged the rounded bacterium a thousand times, it would only be the size of a pinhead. We barely see bacteria by a magnification an ordinary microscope of 100 times, even if we try, we cannot make out anything of their structure. There are normally millions of them together, for they can multiply really fast.

Scientists have found that some bacteria have attached to wavy-looking "hairs" called flagella. The flagella rotate, pushing the bacteria through the water. Others can glide along over surfaces by some little-understood mechanism. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. They are active all the time. Even the bacteria without flagella often bound about in the water. They are pushed here and there, colliding with the watery molecules.

Bacteria cannot be detected because they don't produce bad odor or change the color or texture of the food. Therefore, when people eat the food with many bacteria, they are likely to get hepatitis A, acute gastroenteritis and a host of other illnesses. Many households have refrigerators to prevent from bacteria. Of course, freezing food slows or stops-the growth of bacteria, however, when food is thawed, the bacteria will become reactivated. Bacteria can not be totally destroyed before the food is thoroughly cooked. We need to know that not all bacteria are in connection with illness. Just some bacteria can cause disease. They are called pathogenic bacteria. Fortunately our immune system can protect us from them.

Bacteria are prokaryotes (single cells that do not contain a nucleus). It may seem weird to classify organisms according to such details, but with or without a nucleus is not trivial at all. The division between prokaryotes and eukaryotes (all organisms with a nucleus inside their cells) is of extreme importance in biology, and is the result of a major evolutionary breakthrough. Visit our program tomorrow if you want to know more, thank you.

Which of the following is true according to the first paragraph？

A．Bacteria are as big as a pinhead.

B．Bacteria can not be seen by an ordinary microscope.

C．Bacteria are hard to see because they often live together.

D．Bacteria are very small so they can only be measured in microns.