新概念英语第一册41课中What’s in it?为何不写成What’re in it?

Question

全文是：SAM：Is that bag heavy, Penny?
PENNY：Not very.
SAM：Here! Put it on this chair. What’s in it?
PENNY：A piece of cheese.
A loaf of bread.
A bar of soap.
A bar of chocolate.
A bottle of milk.
A pound of sugar.
Half a pound of coffee.
A quarter of a pound of tea.
And a tin of tobacco.
SAM：Is that tin of tobacco for me?
PENNY：Well, it’s certainly not for me!
请问penny的书包里有这么多东西，为什么用What’s in it，而不用复数形式What’re in it?

Answer 1

都是不可数名词

Answer 2

1、Is it a Korean car or an English car? 2、Is it Japanese or 就比如问你是哪里人一样，会回答I'm Chinese. 宁波环球雅思挺不错的

Answer 3

这是英语习惯用法，在询问者没弄清楚bag里面到底有多少东西的时候就用单数泛指容量，用复数的话就弄巧成拙了。希望能帮到你。