英语完形填空(Aristotle was the first to wacth living things and to .)

Among
the early Greeks,Aristotle was the first to watch living things and
to try to (47=classify ) them to attempt to find out how life begins,
and to write down his (48=observations) .
His
methods of work with the catfish are typical of his (49=不确定?precautions?)
50.float
51.deposits
52.sifficiently
53.disadvantages
54.colleagues
55.inexhaustible
56.refers完整短文原文