David doesn’t give up _______ he has failed in the experiment four times.
#57463
A
if
B
while
C
though
D
since
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---Why is the little boy crying over there? -----He is too short to reach ___ the toy bear ___ the toy car on the shelf?
#55650
A
both …and
B
either …or
C
neither….nor
D
not…but[
—It’s very hot in the room! --_______ the door open?
#55563
A
Why don’t keep
B
Why don’t to keep
C
Why not keep
D
Why not you to keep
Many people believe we will face environmental disasters _________ we completely change the way we live.
#57124
A
but
B
though
C
unless
D
until