(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.
#30046
A
Who
B
It
C
As
D
What
推荐题目
The question _______ we can get enough coal for the winter has not been cleared up yet .
#33883
A
that
B
if
C
which
D
whether
I think you should end it _______ it’s too late, or you may be sorry about it later.
#33286
A
after
B
when
C
until
D
before