51.C 出自”Everyone knows that chickens lay eggs(产卵).“和 ”They include bees,snakes and some sea animals.“
52.A 出自”Animals lay many eggs because other animals may eat the babies.“
53.A 出自” Then they put their eggs in the sand and leave.“和” When the babies come out of the eggs,they must find their own way to the ocean.They must learn how to live on their own.“
54.D 出自”Most eggs have an outside shell(壳)that keeps the growing animal inside safe.“
55.B 通篇来看是篇科普文章.