________ there are living creatures in the outer space as those on Earth hasn't been proved until now.
#30306
A
How
B
When
C
Where
D
Whether
推荐题目
You can’t use my bike _____ you return it to me by the weekend.
#31644
A
if not
B
unless
C
because
D
though
(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
News has spread ______Mr. Smith has two people over him in this department.
#32124
A
while
B
that
C
when
D
as