[单项选择]A) They learned to save as thrifty as their parents.
B) They spend money quickly and impulsively to avoid higher prices.
C) They put most of theft money into their savings accounts.
D) They spend some money and save some.

[填空题]The word conservation has a thrifty meaning. To conserve is to save and
protect, to leave what we ourselves enjoy in such good condition as others (53)______
may also share the enjoyment. Our forefathers had no idea that human population
would increase faster than the supplies of crude materials. Most of them, even (54)______
until very recently, have the foolish idea that the treasures were "limitless"
and "inexhaustible". Most of the citizens of early generations knew little or (55)______
nothing about the complicated and the delicate system that runs all through the
nature, which means that, as in a life body, an unhealthy condition of one part (56)______
will sooner or later be harmful to all others. (57)______
Fifty years ago nature study was not part of the school work. Scientific (58)______
forestry was a new idea; timber was still cheap