The research they had been devoted to ______ to be of great value to the cancer patients.
#103621
A
is proved
B
proves
C
has proved
D
proved
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—It’s only ten minutes’ walk; I could have got there on foot. — Yes. A taxi _______ not at all necessary.
#102919
A
was
B
had been
C
has been
D
is
It’s said that the early European playing-cards ______ for education.
#99874
A
have designed
B
were designed
C
have been designed
D
were being designed