They are good friends. is no wonder that they know each other so well.
A. This
B. That
C. There
D. It
网友回答
A. This
B. That
C. There
(答案→)D. It
解析：it’s no wonder that… 意为“难怪……”、“……不足为怪”，为英语固定表达，其中的 it’s 也可省略，即只说 No wonder that…。如：
No wonder (that) he didn’t want to go. 难怪他不想去。