_____ used to be said that Turkey was virtually the master of th

_____ used to be said that Turkey was virtually the master of the Black Sea.
A、That
B、It
C、What
D、They
【正确答案】：B
【题目解析】：此句的意思是曾经有传言土耳其是黑海的真正主人。That后面的分句 是该句的实际主语，因为过长后置用it来代替作为形式主语。