16. The thread of my kite broke and it flew away. I had told you it would easily break ________it was the weakest.
A. when B. where C. unless D. since
17. The crowd started cheering ______ he rose to speak.
A. as B. since C. till D. where
18. I had worked here ______ you came here. But I shall leave for England ______.
A. before long， before long B. before long； long before C. long before， before long D. long before； long before