I was exhausted when I reached home, and I flung myself down on the front steps to （）.

A:discover B:recover C:dissolve D:retreat

In 1575--over 400 years ago the French scholar Louis Le Roy published a learned book in which he voiced despair over the changes caused by the social and technological innovations of his time, what we now call the Renaissance. We, also, feel that our times are out of joint; we even have reason to believe that our descendants will be worse off than we are.
The earth will soon be overcrowded and its resources exhausted. Pollution will ruin the environment, upset the climate and endanger human health. The gap in living standards between the rich and the poor will widen and lead the angry, hungry people of the world to acts of desperation including the use of nuclear weapons as blackmail. Such are the inevitable consequences of population and technological growth if present trends continue.
The future is never a projection of the past. Animals probably have no chance to escape from the tyranny of biological evolution, but human beings are blessed with the freedom of social evolution. For us, trend is not destiny (fate). The escape from existing trends is now facilitated by the fact that societies anticipate future dangers and take preventive steps against expected changes.
Despite the widespread belief that the world has become too complex for comprehension by the human brain, modern societies have often responded effectively to critical situations. The decrease in birth rates, the partial prohibition of pesticides and the rethinking of technologies for the production and use of energy are but a few examples illustrating a sudden reversal of trends caused not by political upsets or scientific breakthroughs, but by public awareness of consequences.
Even more striking are the situations in which social attitudes concerning future difficulties undergo rapid changes before the problems have come to pass -- witness the heated arguments about the problems of behavior control and of genetic engineering even though there is as yet no proof that effective methods can be developed to manipulate behavior and genes on a population scale.
One of the characteristics of our times is thus the rapidity with which steps can be taken to change the orientation of certain trends and even to reverse them. Such changes usually emerge from grass root movements rather than from official directives.
The best illustration of the meaning of "trend is not destiny" in paragraph 3 is that

A:human beings are blessed with the freedom of social evolution. B:the world has become too complex for human beings to modify. C:preventive steps against catastrophes are difficult to be adopted. D:the earth will soon be overcrowded and its resources exhausted.

Tom was too exhausted to wake easily （　）

A:when once sleeping B:when once asleep C:when he was once sleeping D:when he once slept

众所周知, our natural resources will be exhausted in the near future.

As is well known to all

share diligence remove enlighten persist in be patient with feel exhausted put ...into practice

Even ______ exhausted, the young actor continued to perform energetically.

A:if B:as C:when D:since

The exhausted mother smiled at the wail of her newborn baby.

A:sad B:gloomy C:tired D:happy

The quantity of cooled air delivered by an air conditioning unit should _____ the sum of the quantity of air re-circulated to the unit and the quantity mechanically exhausted.

A:balance B:not balance C:be more than D:be less than