They were surprised that a four-year-old boy should work out such a difficult problem ____ they themselves couldn’t.
#80212
A
once
B
then
C
while
D
if
推荐题目
Roger had just walked into his office and that was when he was told that his plan had finally been approved. Which of the following can be instead of the underlined(划线的) part to make the sentence better.
#31243
A
and then they told him
B
when it was learned by him
C
and then he learned
D
when he learned
._____ you arrive in Ireland, you will quickly find yourself on the beautiful country roads.
#34519
A
Since
B
While
C
Once
D
Until
_______ many people first go to the Internet for information, it is not always the best place for what you need.
#33612
A
As
B
Since
C
When
D
While
David knocked at the door for nearly half an hour______Mary opened it, unwilling.
#30820
A
when
B
while
C
until
D
before