6228 - Intermediate\Upper-Intermediate Test:4 - The transistor ______ in 1948. As a result of this, both the size and the cost of electronic equipment______ greatly

The transistor ______ in 1948. As a result of this, both the size and
the cost of electronic equipment______ greatly reduced.
had been invented / has been
was invented / have had
was invented / have been
had invented / will be
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