【C19】A．because ofB．becauseC．forD．from

__ you are tired, you had better sit down.A.because ofB.AsC.ForD.when

【23】A．ofB．withC．forD．in

【C19】A．partly becauseB．mainly becauseC．not becauseD．not because of

【C19】A．ofB．atC．inD．for

【C5】A．ofB．withC．forD．to

20．A．ofB． toC． forD． from