a group of 的用法

a group of 后面只能接可数名词
比如说：
A group of people are on a tour.
一群人在参观
Would you chaperone a group of juvenile detention center inmates on a day trip to the zoo?
你能否陪同青少年感化中心的少年犯去动物园玩一天?
A large group of chimpanzees was feeding.
一大群黑猩猩在吃东西.
A group of us are going up to London for the day.
我们有些人要去伦敦一天.