题目

My favorite animals are elephants. Elephants are   1    living animals on land. There are two kinds of elephants--African elephants and    2    elephants. African elephants are larger than Indian elephants, and they have  3  ears.Elephants have to eat    4     because they are so big. One elephant can eat between 100    5  1,000 pounds     6    grass in a day! They can live for 60--70 years. There are no bones in the back of    7  feet, only fat. Elephants walk on tiptoe. They can move quietly and walk in the mud   8.Elephants grow tusks. The tusks areA. 细胞质中仅含有核糖核酸B. 组成淀粉、糖原、纤维素的单体都是葡萄糖C. 多肽链在核糖体上一旦形成便具有生物活性