Question

---How amazing it is that astronauts are exploring outer space! 

  ---t’s a challenge, I guess,         man against nature. 

A. of             B. for               C. by              D. about

Answer 1

A

解析:

考查介词。应答句中的I guess是插入语，因此所填介词与challenge连用，表所属，用of，选A。