I felt puzzled to find this kind of plants growing well deep in the cave. Normally they ________ without sunlight.

1. A.
   mustn't grow
2. B.
   couldn't have grown
3. C.
   can't grow
4. D.
   may not have grown

I felt puzzled to find this kind of plants growing well deep in the cave. Normally they ________ without sunlight.

[　　]