【实例解析】

1. (2004年北京市海淀区中考试题)
You will stay healthy _______ you do more exercise, such as running and walking.
A. if B. how C. before D. where
答案：A。该题考查的是引导状语从句的从属连词的选择。从意思上看，从句应是一个条件状语从句，在这四个选项中只有if能引导条件状语从句，所以选A。
2. (2004年江西省中考试题)
---Shall we go on working?
---Yes, _________ I prefer to have a rest.
A. when B. if C. because D. though
答案：D。该题考查的是引导状语从句的从属连词的选择。从意思上看，只有选though才能说得通。
3. (2004年徐州市中考试题)
None of us knew what had happened _________ they told us about it.
A. when B. until C. after D. though
答案：B。该题考查的是引导状语从句的从属连词选择。本句的意思是“在……以前我们没人知道这件事。”要表达着一意思应用“not…until” 这一句型。
4. (2004年泉州市中考试题)
---I hope you’ll enjoy your trip, dear!
---Thank you, mum. I’ll give you a call _________ I get there.
A. until B. as soon as C. since D. till
答案：B。该题考查的是引导状语从句的从属连词的选择。本题的意思是“一到那里，我就给你打电话。”要表达这个意思应选用as soon as。