Question

______ for something, a receipt is given to you

1. A.
   Paying
2. B.
   Having paid
3. C.
   When you have paid
4. D.
   To be paying

Answer 1

C
考查非谓语动词。pay和give有先后关系，应该用完成时；排除A、D；B项缺少逻辑主语，故排除；C项符合题意。故选C。