There are three bedrooms in the house, ________ is Mary’s．

1. A.
   the smallest of which
2. B.
   the smaller of which
3. C.
   the smallest of them
4. D.
   the smallest of all

There are three bedrooms in the house, _________ is Mary’s．

A. the smallest of which   B. the smaller of which  C. the smallest of them   D. the smallest one