It will be some years before some foreign doctors change the impression they have _____Chinese medicine, _____, in their opinion, is nothing but raw herbs and not effective at all in treating diseases.

 It will be some years before some foreign doctors change the impression they have _____Chinese medicine, _____, in their opinion, is nothing but raw herbs and not effective at all in treating diseases.

It will be some years before some foreign doctors change the impression they have _________ Chinese medicine, _________, in their opinion, is nothing but raw herbs and not effective at all in treating diseases．

1. A.
   for; which
2. B.
   on; what
3. C.
   to; that
4. D.
   on; which

It will be some years before some foreign doctors change the impression they have _____Chinese medicine, _____, in their opinion, is nothing but raw herbs（药草） and not effective at all in treating diseases．

A．for; which       B．on; what      C．to; that        D．on; which