排除法
amount of sth (used esp with [U] ns 尤与不可数名词连用):total sum or value 总数; 总额; 总值
a bill for the full amount 全部金额的帐单
Can you really afford this amount?你真付得起这个总数吗?
习语any amount of sth a large quantity of sth,表示大量
He can get any amount of help.他能得到大量的帮助.
people为可数名词,故排除B和D.
those特指那些人,而number of people指许多人,并没有特指的含义,故A排除