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：C 句意：他们都知道老板已经违背了将给他们涨工资的诺言。第一空处，It作形式主语，指代真正的主语“that the boss had broken his promise...”。promise之后是其同位语从句，从句句意完整且不缺成分，所以填that。