which of the subjects that you are studying is the most diffcult _英语解答

which of the subjects that you are studying is the most diffcult
1 为什么用of 不用可以么
2 that 可以省略么

人气：108 ℃　时间：2020-05-08 04:52:17

解答

of 要用,subjects 多个中的一个,与后面 is the most 单数呼应；
that 可以省略.