___ help the people in the snowstorm in the south made him worried.

  A. Not known how to               B. Unknown what to do to

  C. His knowing not how to         D. His not knowing how to

________ help the people in the snowstorm in the South made him worried.

A. Not known how to                  B. Unknown what to do to         

C. His knowing not how to           D. His not knowing how to

________ help the people in the snowstorm in the South made him worried.

A. Not known how to 　　　　 B. Unknown what to do to

C. Our knowing not how to 　 D. Our not knowing how to

______ help the people in the snowstorm in the South made him worried.

1. A.
   Not known how to
2. B.
   Unknown what to do to
3. C.
   His knowing not how to
4. D.
   His not knowing how to