Didn’t ever occur to you what the source of this saying I just quoted is?
A. this
B. it
C. that
D. one
网友回答
A. this
(答案→)B. it
C. that
D. one
解析：考查it作为形式主语。本题的it是一个形式主语，真正的后足浴是后面的主语从句what the source of this saying I just quoted is。本题也是一个固定句型：it occur to sb …某人突然想起某事。故B正确。