【C6】A．butB．orC．howeverD．unless

A．otherwiseB．certainlyC．howeverD．therefore

【C5】______A．butB．orC．because

【C2】A．butB．orC．andD．while

【C6】A．thereforeB．subsequentlyC．howeverD．furthermore

【C6】A．butB．andC．becauseD．though

【C6】A．andB．orC．forD．but