Human and Culture
Human beings are animals. We breathe, eat and digest, and reproduce the same life processes common to all animals. In a biological laboratory, rats, monkeys, and humans seem very much the same.
However, biological understanding is not enough: (51) itself, it can never tell us what human beings are. (52) to our physical equipment—the naked human body—we are not an (53) animal. We are tropical creatures, nearly hairless and sensitive to cold. We are not fast and have neither claws nor sharp teeth to defend ourselves. We need a lot of food but have almost no physical equipment to help us get it. In the purely physical (54) , our species seems a poor (55) for survival.
But we have survived—survived and multiplied and (56) the earth. Some day we will have a (57) living on the moon, a place with neither air nor water and with temperatures that turn gases into solids. How can we have done all these things？ Part of the answer is physical. In spite of its limitations, our physical equipment has some important (58) . We have excellent vision and hands that can (59) objects with a precision unmatched by any other (60) . Most importantly, we have a large brain with an almost (61) number of neural connections.
We have used this physical equipment to create culture, the key to our survival and success. If we live in the Arctic, we supply the warmth our tropical bodies need (62) clothing, shelter, and (63) heat. If a million people, want to live in a desert that supplies natural food for only a few hundred, we find water to grow food and (64) deficits by transporting supplies from distant places. Inhabitants of our eventual moon colony will bring their own food and oxygen and then create an artificial earth environment to supply necessities. With culture, we can overcome our natural limitations.
It was not always (65) . Our distant ancestors were just animals, faced with the limits of their physical equipment. They had no culture and lacked the physical capacity to use it.
(51)

A. On
B. With
C. For
D. By