听力原文：W: Welcome to our program. Today Prof. Johnson is going to talking about solar po

M: Thank you. As you can see, little by little, Americans are turning to solar power, tapping the strength of the sun for energy.

W: Yeah, that's true. Sunlight has already been used for heating or cooling homes and office buildings in the sunny south.

M: Experts say all signs point to the birth of the solar energy industry. Right now, an increasing number of companies are selling solar collector panels to heat and cool homes or to heat water. The glass and metal panels each cost from ＄100 to more than ＄500, and the three or four-bedroom home usually requires a dozen or more. They look like sandwiches. They are usually placed in rooftops. Nobody knows how many have been sold, and in addition, many people have built their own units. It has been estimated that solar power equipment will be a $1.3 billion industry by 1995, and more than a million homes will use sunlight for heat, air conditioning or to generate electricity, both in the cities and in countryside.

W: Wow! That is really big business.

What do we learn about the use of solar energy in the U. S. ？

A．It is very well established.

B．It is relatively new.

C．It is found in one million homes.

D．It is being rapidly expanded.