English is essential in this job. All the telephonists speak it. If they (not know)____ English, they (not understand)______ half the callers
Question: English is essential in this job. All the telephonists speak it. If they (not know)____ English, they (not understand)______ half the callers.
A. didn't know - would not understand
B. hadn't known - would not understand
C. didn't know - did not understand
D. didn't know - would have not understood