He is so clever to work out the problems no matter they are.
- A.how difficult
- B.what difficult
- C.how difficulty
- D.what difficulty
答案
正确答案：A
知识点：感叹句
根据语境，“无论他们多么困难”可以表达为no matter how difficult they are或however difficult they are。故选A。注意difficult是形容词，difficulty是名词。
略
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