【C2】A．so thatB．becauseC．unlessD．though

A．becauseB．althoughC．unlessD．so

【C15】A．andB．becauseC．butD．so

【C13】A．alsoB．becauseC．asD．so

It was raining and_____ we went home.A. thatB. becauseC. so

Doctors won t operate on the patient______absolutely necessary.A．whenB．ifC．unlessD．though

【C3】A．ButB．BecauseC．AndD．So