A major reason for conflict in the animal world is territory. The male animal 【C1】______ a

n area. The size of the area is 【C2】______ to provide food for him, his 【C3】______ and their off- spring. Migrating birds, for example, divide up the best 【C4】______ in the order of" first come, first 【C5】______ " The late arrivals may acquire 【C6】______ territories, but less food is available, or they are too close to the 【C7】______ of the enemies of the species.

When there is 【C8】______ over territory, animals will commonly use force, or a 【C9】______ of force, to decide which will stay and which will go.

It is interesting to note, however, that animals seem to use only the 【C10】______ amount of force necessary to drive away the 【C11】______ .

There is usually no killing. In the 【C12】______ of those animals which are capable of doing each other harm, there is a 【C13】______ .for the losing animal to show the winning animal that he wishes to submit. When he shows this, the 【C14】______ normally stops fighting. Animals (especially birds), which can easily escape from conflict seem to have no 【C15】______ against killing, and equally no mechanism for 【C16】______ .

The 【C17】______ bird simply flies away. However, if two doves are 【C18】______ in a cage, and they start fighting, they will continue to fight until one kills the other. We all think of the dove as a 【C19】______ of peace and, in its natural habitat, it is peaceful. But the" peace" mechanism does not 【C20】______ in a cage.

【C1】

A．establishes

B．builds

C．founds

D．erects