________ is known to us is that the old doctor, for ________ life was hard in the past, still works very hard in his late life．

1. A.
   As; whom
2. B.
   What; whom
3. C.
   It; whose
4. D.
   As; whose

 ______ is known to us is that the old doctor, for ______ life was hard in the past, still works very hard in his late life.
A. As; whom     B. What; whom     C. It; whose     D. As; whose

_________ is known to us is that the old doctor, for _________ life was hard in the past, still works very hard in his late life.
A. As; whom     B. What; whom     C. It; whose     D. As; whose