Up to now, our society ________ with limited living space and a shortage of natural resources.
#63760
A
has been challenged
B
is being challenged
C
is challenging
D
has challenged
推荐题目
Barrack Obama __________ President of the United States since 2010.
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A
became a
B
has become a
C
has turned
D
has been
The house is dirty because it ________ since they moved out.
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A
doesn't clean
B
isn't cleaned
C
hasn't cleaned
D
hasn't been cleaned
We complained to the travel agency about the horrible service during our trip，but no one has________by now.
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A
responded
B
deserved
C
recovered
D
survived
Tom ________ in the library every night over the last three months.(2011·北京)
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A
works
B
worked
C
has been working
D
had been working