다음 문장이 들어갈 위치로 가장 적절한 것은? We can in consequence establish relations with almost all sorts of them. Reptiles and fish may no doubt be found in swarms and shoals; they have been hatched in quantities and similar conditions have kept them together. In the case of social and gregarious mammals, the association arises not simply from a community of external forces but is sustained by an inner impulse. They are not merely like one another and so found in the same places at the same times; they like one another and so they keep together. This difference between the reptile world and the world of our human minds is one our sympathies seem unable to pass. ( A ) We cannot conceive in ourselves the swift uncomplicated urgency of a reptile's instinctive motives, its appetites, fears and hates. ( B ) We cannot understand them in their simplicity because all our motives are complicated; ours are balances and resultants and not simply urgencies. ( C ) But the mammals and birds have self-restraint and consideration for other individuals, a social appeal, a self-control that is, at its lower level, after our own fashion. ( D ) When they suffer they utter cries and make movements that rouse our feelings. We can make pets of them with a mutual recognition. They can be tamed to self-restraint towards us, domesticated and taught.