He is really an excellent doctor and he is _____ to becoming an expert in this field

1. A.
   in a way
2. B.
   by the way
3. C.
   on the way
4. D.
   under the way

.He is really an excellent doctor and he is _____ to becoming an expert in this field.

A. in a way                       B. by the way             C. on the way             D. under the way