Human beings are animals. We breathe, eat and digest, and reproduce the same life【21】_____

Human beings are animals. We breathe, eat and digest, and reproduce the same life 【21】______ common to all animals. In a biological laboratory, rats, monkeys, and humans seem very much the same.

However, biological understanding is not enough. 【22】______ itself, it can never tell us what human beings are. 【23】______ to our physical equipment -- the naked human body -- we are not an 【24】______ animal. We are tropical creatures, 【25】______ 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 【26】______ , our species seems a poor 【27】______ for survival.

But we have survived -- survived and multiplied and 【28】______ the earth. Some day we will have a 【29】______ 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. 【30】______ its limitations, our physical equipment has some important 【31】______ . We have excellent vision and hands that can 【32】______ objects with a precision unmatched by any other 【33】______ . Most importantly, we have a large brain with an almost 【34】______ number of neural 【35】______ .

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 【36】______ clothing, shelter, and 【37】______ 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 【38】______ 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 【39】______ Our distant ancestors were just animals, faced with the limits of their physical equipment. They had no 【40】______ and lacked the physical capacity to use it.

【21】

A．processes

B．acts

C．modes

D．procedures