Question

Speak clearly, ________ they may understand you.

1. A.
   because
2. B.
   until
3. C.
   so that
4. D.
   unless

Answer 1

C
该祈使句是一个含有目的状语从句的主从复合句，从句表示主句动作的目的。四个选项的从属连词，只有so that可以引导目的状语从句。