21. Though ______, running does us much good.

A tired             B. tiring           C. we tired            D. it gets tired

22. Do you consider it any good ______ psychology?

A. to learn         B. learning         C. learned          D. having learned

23. Although ______ of danger, tourists can’t help taking photos near the cliff.

A. having warned    B. warning          C. warned           D. warn

24. ______ with so much trouble, we failed to complete the task on time.

A. Faced            B. Face             C. Facing           D. To face

25. There’s a note pinned to the window ______ when the shop will open again.

A. saying           B. says             C. said             D. having said