【C2】A．howeverB．althoughC．andD．while

【C2】A．afterB．whenC．whileD．once

【C2】A．butB．orC．andD．while

【C4】A．whenB．althoughC．butD．while

【C2】A．WhenB．AsC．WhileD．Since

【C2】A．sinceB．ifC．asD．while

【C8】A．butB．while "C．andD．whereas