Question

historians suggest that biological warfare is first being used in 1347, when the mongols intentionally spread the black plague to exterminate their enemies. choose 1 answer: a no change b was first used in c was first using d was first being used in

Explanation:

The sentence is about an event in 1347 (past). The original "is first being used" (present continuous) is wrong. We need past tense. "Was first used in" (simple past passive) is correct as it shows the action (use of biological warfare) was done to the subject (biological warfare) in the past. "Was first using" (past continuous active) is wrong as biological warfare can't 'use' itself. "Was first being used in" (past continuous passive) is more for an ongoing action in the past, but here it's a one - time event.

Answer:

B. was first used in