强调句可以省略that吗？

在口语中，It is / was ... that 强调句中的that 可以省略。比如：
What is it you want me to do? （假如不省略that，句子是： What is it that you want me to do ?）
所以，上面那道考试试题和答案都是正确的：
make out后引导的是含有 It is / was ... that 强调的宾语从句，其中的 that 省略了。假如填入答案和 that ，就可以非常不错理解了：
His writing is so confusing that its difficult to make out ______ what ______ it is that he is trying to express.