David didn’t give up ______ he had failed in the experiment four times.
#58224
A
if
B
while
C
though
D
since
推荐题目
— What’s your plan for this weekend? — We will go for a picnic by the river _______ it rains.
#56007
A
unless
B
if
C
but
D
because
—All the isatis root（板蓝根） is sold out!—People are crazy! experts say there is no use eating isatis root to preventH7N9, some people still don’t believe it.
#56593
A
Although
B
Unless
C
As a result
D
In order that
—How can I learn English well?—You will learn it well ________ you practice speaking it often.
#56660
A
unless
B
as for
C
as soon as
D
as long as