请从方框中选择合适的单词填入短文中，使其意思完整（每词限用一次，其中有两个

多余选项）。

classroom, playground, tired, down, small, gives, lying

     We are in the    l    now. We are having a PE lesson. Mr Smith   2   us some orders. Look, we

are jumping up and   3   ten times. David can't do it, because he is too   4  . So he is   5   on the

grass now, having a rest.

点彩红细胞胞质中的颗粒为（）.

A.残存变性的DNA

B.残存变性的RNA

C.残存变性的脂蛋白

D.核糖体

E.金属颗粒沉淀