So far, the moon is the only one of the heavenly bodies in space ______ reached by manned spaceships.

So far, the moon is the only one of the heavenly bodies in space ______ reached by manned spaceships.

1. A.
   that has been
2. B.
   what have been
3. C.
   which has been
4. D.
   that have been

So far, the moon is the only one of the heavenly bodies in space ______ reached by manned spaceships.

   A. that has been    B. what have been        C. which has been  D. that have been

So far, the moon is the only one of the heavenly bodies in space ______ reached by manned spaceships.