When the old man saw some litter on the ground he quickly .A. picked it up B. picked up

问题补充：

When the old man saw some litter on the ground, he quickly .

A. picked it up

B. picked up it

C. picked them up

D. picked up them.

答案：

(答案→)A. picked it up

B. picked up it

C. picked them up

D. picked up them.

解析：本题的含义是当老人看到地上的垃圾，他会很快地把它们捡起来，pick up sth为此意，sth为代词，应放在pick和up之间，垃圾为不可数名词用it，故本题选A。