Two __took part in the activity during the summer hoilday

问题描述:

Two __took part in the activity during the summer hoilday
答案是hundred old people ,我自己选了hundreds old people...

hunderd old people 是对的
前面有数词,hundred用原型,而且后面不用of
eg.three hunderd people
前面没有数词,则用hundreds of,意为“成百上千的”
eg.hundreds of people