The industrial societies have been extremely productive during the last two centuries. The

economic advance has been remarkable. During this relatively short period of time, greater changes in people's living conditions have occurred than in the thousands of years which preceded.

During the past 200 years the world population has increased 6 times, the annual world output has increased 80 times, and the distance a person can travel has gone up 1,000 times. There has also been much recent progress in art, culture, learning, and science. Such changes have led to a high rate of production and growth of the economy.

Economists fear that within the next 100 to 150 years, the earth's resources will become very scarce. Their fears are partly justified, but we should not be afraid. Industrial civilization adapts to new knowledge. By advancing knowledge, we not only create new forms of resources, but we also find ways to economize their use. Advanced modern knowledge can feed the hungry people of the world and improve their standard of living.

The figures in the second paragraph are used for the following purposes EXCEPT______.

A．prediction.

B．contrast.

C．definition.

D．explanation.