观察法是收集原始数据的一种方法，下列各项中，（）不是使用该方法的必要条件。A．所需信息必须是

Which of the following is the main idea of this passage？

A．Fire can help people in many ways.

B．Fire can be both helpful and dangerous.

C．Fire can burn things and people.

D．We must be careful with matches.

Which of the following is the main idea of this passage？

A．Fire can help people in many ways.

B．Fire can be both helpful and dangerous.

C．Fire can bum things and people.

D．We must be careful with matches.

Which of the following is the main idea of this passage？

A．Fire can help people in many ways.

B．Fire can be both helpful and dangerous.

C．Fire can burn things and people.

D．We must be careful with matches.

The main idea of this passage is that .

A．there are many disadvantages of living in cities

B．people's preference for living in cities is wrong

C．the living conditions of cities are worse than those of countries

D．measures should be taken to improve the living conditions in cities

The main idea of this passage is that satellites aye now used in______．

A．taking pictures of the atmosphere

B．receiving pictures of the atmosphere

C．doing other work in many ways

D．weather forecasting

What is the main idea of the passage？

A．Venice is sinking.

B．Venice is a dream like city.

C．It is not easy to change the timetable of the public bus service.

D．There are many historic sites in Venice.

The main idea of this passage is______.

A. it is likely to make an enemy of your admirer

B. there are many solutions to the problems of dating

C. an admirer has feeling every bit as sensitive as our own

D. it is possible to discourage an admirer without hurting his feelings

What is the main idea of this passage？

A．Student employment is a major cause of educational decline.

B．American education is declining.

C．There are many reasons for educational decline.

D．Measures should be taken to stop student employment.

The main idea of the passage is ______.

A．even Americans are surprised at the big differences among themselves

B．there are many differences in character in different parts of the USA

C．there are many reason for the differences

D．stereotypes about people are not necessarily true