问题
选择题
(2014·河南豫北三校联考)________is well known to everyone，I should say，is that a man becomes learned by asking questions.
A．Who
B．It
C．As
D．What
答案
答案：D
考查名词性从句。句意为：我应该说，众所周知要长学问，就得多问。句中的I should say是插入语，因此空处应填引导主语从句的连词What。
答案： D