问题
选择题
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
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。