（D）
The desire to make explorations is born with man. Wherever his imagination goes, man also has a strong wish to go. A large part of human history is connected with the exploration of the world in which we live. Again and again people have set out with surprising courage and patience to look into unknown regions and lands to see what had not yet been seen, to make known the unknown. With kites, balloons and aircraft they left the ground to pass through the lower atmosphere. Now the outer space receives their attention.
Why should man take the trouble of exploring space? It is hard to list the specific practical benefits that will result in. But one knows, from past experience in other areas, that man will surely see and discover new things in space that will increase our scientific knowledge, and this new knowledge will find its way into valuable practical uses. What we learn about man himself, from his experience in space, and from the effects of space and the space flight environment on him, will be extremely valuable. The new techniques developed to carry out the exploration of space, and to keep man alive in space, will certainly find practical uses in everyday life in some way. The areas that will benefit are manifold. They include communication, generation of power, transportation and travel, food production, materials, fuels and many others. But to say exactly what the practical results will be is almost impossible.
67. The main idea of the first paragraph is that __________.
A. man often goes wherever his dreams go
B. man desires to explore what is unknown
C. man is no longer interested in the study of the land and sea now
D. man's history is his exploration of the world
68. The word "manifold" in the second paragraph probably means ________ .
A. of value       B. of use       C. in a way      D. in many ways
69. The author seems to be in favor of ____.
A. the exploration of space
B. doubting the necessity of the space exploration
C. exploring more in space than in sea         
D. his experience in space
70. In the last sentence of paragraph 2 ,the phrase "practical results" refers to the results ______.
A. that can be made use of
B. that can be learned as knowledge
C. that are obtained from experience         
D. helping us make further exploration