1.You will stay healthy _______ you do more exercise, such as running and walking.

A. if B. how C. before D. where

答案：A

解析：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. My uncle has been taught in this school _______ he was twenty years old.

A. since B. for C. until D. after

答案：A

解析：考查since引导的时间状语从句。结合题意"我的叔叔自从二十岁以来就一直在这所学校教书"可排除B、C、D三项，选A。

3.______ they may not succeed, they will try their best.

A. Though B. When C. Because D. Unless

答案： A

解析：考查though引导的让步状语从句。结合题意"尽管他们不可能成功，但是他们将尽全力"可排除B、C、D三项，故正确答案为A。

4.--Shall we go on working?

---Yes, _________ I prefer to have a rest.

A. when B. if C. because D. though

答案：D

解析：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。
 

5. None of us knew what had happened _________ they told us about it.

A. when B. until C. after D. though

答案：B

解析：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。

以上就是本期的英语巩固测试题。每天练习一点，坚持就有成果。加油练习吧。