' This is fine. ' I wouldn't say this.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Cup cake' Carl waited for a cab while he was talking on his mobile.'This is fine.
Cup cake' Carl waited for a cab while he had been talking on his mobile.'I wouldn't say this.
Cup cake' Carl waited for a cab while he was talking on his mobile.'As the two things are happening at the same time, there is no reason at all for a past perfect form.
fivejedjonDid he talk on his mobile and then begin to wait for a cab?Yes.
fivejedjonIs there any connection between his talking on the mobile and his waiting for a cab?In succession. (His talking following, without interruption, his waiting for a cab.)