The correct answer is A. The telephone was ringing several times before I answered it.
The other options are incorrect because they do not accurately describe the order of events. Option B, has rung, implies that the telephone rang once and then stopped ringing before I answered it. Option C, had rung, implies that the telephone rang before I answered it, but it is not clear how long ago it rang. Option D, would ring, implies that the telephone is about to ring, but it has not rung yet.
The sentence “The telephone was ringing several times before I answered it” describes a series of events that happened in the past. The first event was that the telephone rang. The second event was that I answered the telephone. The two events happened in the order that I described them. The telephone rang before I answered it.
I hope this explanation is helpful. Let me know if you have any other questions.