A. once B. whileC. since D. unless

【C12】A．thenB．whileC．sinceD．where

【C15】A．WhenB．WhileC．AsD．Unless

______I was talking to Barbara, I learned that Tony was in hospital.A．UnlessB．WhileC．Since

You’ll have more chances of promotion ______ you work hard.A、sinceB、whileC、asD、once

【C2】A．WhileB．AsC．SinceD．Unless

___________[A] Since [B] If [C] Unless [D] While