The population of the United States is only 6% of the world’s population, but Americans (21) one third of all the energy (22) in the world. This fact alone says that Americans need to use less energy. And because the price of energy had been rising very rapidly (23) the limited supplies of oil in particular, Americans are becoming aware to the need to (24) energy. In California we have a California Energy Commission which has set up in the past five years to (25) plan for our future energy use. We have (26) laws in California to help us conserve energy. First of all, our houses in California have been very (27) of energy in the past. They were not (28) very carefully and so the heat would go out of the house very rapidly. Now we require that the homes have a (29) level of insulation, and so the homes built now are much more (30) .
(31) , in transportation (32) a large percentage of oil energy is used, we need to develop more public transportation. In China, of course you have a very good public transportation system. And it is a (n) (33) for the kind of thing we need to develop more in the United States. Automobiles are also becoming more (34) . The smaller automobile with efficient engine can help to conserve a large amount of energy along with planning our (35) more carefully.
Many different studies have shown that we could (36) our energy consumption by (37) half or two thirds and still have the (38) quality of life. And many different types of technologies are currently being researched as to (39) they can be built to use (40) energy and still supply the same service.

23().

A．largest
B．smallest
C．maximum
D．minimum