Experiments of this kind _______in both the U.S. and Europe well before the Second World War started.
#100664
A
have conducted
B
have been conducted
C
had conducted
D
had been conducted
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As we all know, the world’s supplies of oil_________ up with the development of industry and the increase of cars.
#104232
A
are being used
B
are using
C
have used
D
have been used
With Chang'e-3 successfully landing, China becomes the third country in the world that _______ on the moon.
#99884
A
lands
B
has landed
C
landed
D
was landing
—Mike, why didn’t you come yesterday? —I __________, but I had an unexpected visitor.
#103200
A
had
B
would
C
did
D
was going to
In such a fierce competition, a person has to make every effort if he ______ .
#104971
A
has succeeded
B
is to succeed
C
would succeed
D
will succeed
--- I ____ so busily recently that I ____ no time to help you with your maths.---That’s OK. I can manage it by myself.
#100194
A
had been working; had had
B
have been working; had
C
have been working; have
D
am working; will have