The achievements of the greatest minds in science could never have been reached________ the patient work of hundreds of others．

1. A.
   were it not for
2. B.
   had it not been because
3. C.
   had it not been for
4. D.
   if it had not been

The achievements of the greatest minds in science could never have been reached________ the patient work of hundreds of others．

A．were it not for                B．had it not been because

C．had it not been for      D．if it had not been