【C15】A．UnlessB．IfC．BecauseD．Since

【C19】A．asB．ifC．becauseD．while

【C6】A．UnlessB．IfC．ThoughD．As

（) you work hard, you will certainly succeed.A. ThoughB. IfC. BecauseD. For

【C15】A．unlessB．so thatC．provided thatD．in order that

【C6】A．unlessB．ifC．asD．since

【C10】A．asB．ifC．becauseD．while