was known to them that the boss had broken his promise he would give them a rise.
A. What; what
B. It; which
C. It; that
D. As; that
网友回答
A. What; what
B. It; which
(答案→)C. It; that
D. As; that
解析：这里that引导的主语从句是句子的真正主语，所以需要It作形式主语；在主语从句中，又包含一个同位语从句，引导词在同位语从句中不作任何成分，且无实际意义，故用that引导。