Q356
Although manufacturers . . . . . . . . electric cars as prototypes for a number of years now, it will be a long time before they . . . . . . . . common.
A.
produced/are becoming
B.
have been producing/become
AnswerC.
produce/will become
D.
are producing/became
E.
were producing/will have become
Answer: Option B
Solution
Answer: Option B
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