【C13】A．WhenB．SinceC．AlthoughD．Unless

【C18】A．BecauseB．IfC．AlthoughD．Unless

【C13】A．whenB．whatC．thatD．if

【C17】A．WhenB．HoweverC．AlthoughD．In case

【C15】A．WhenB．WhileC．AsD．Unless

【C13】A．whenB．ifC．beforeD．since

Hardly had we got on the bus______it began to rain.A．whenB．sinceC．butD．before