The transistor in 1948. As a result of this, both the size and the cost of electronic equipment greatly reduced.

was invented / have been

had been invented / has been

was invented / have had

had invented / will be

উত্তর সিলেক্ট করলে সঠিক ও ভুল দেখাবে।

ব্যাখ্যা ও সঠিক সমাধান

উত্তর: was invented / have been

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