【C7】A．howeverB．thoughC．asD．when

【C7】A．BecauseB．ForC．WhileD．When

【C7】A．althoughB．becauseC．only ifD．when

【C7】A．ButB．ThoughC．MoreoverD．Nevertheless

Hard______they tried, they failed to climb to the mountain topA．ifB．when.C．asD．since

【C7】A．SinceB．BeforeC．AsD．If

【C7】A．howeverB．meanwhileC．thereforeD．moreover