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。例如：
What is it you want me to do? (张道真主编《现代英语用法词典》第792页)（如果不省略that，句子是： What is it  that you want me to do ?）
所以，上面那道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。如果填入答案和 that ，就能够很好理解了：
(2011安徽, 33) His writing is so confusing that it’s difficult to make out ______ what ______ it is that he is trying to express. (what是被强调的成分，作 express  的宾语，因为 what 是疑问词，所以移到 it 的前面了)