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:
Choose 1 answer:
(Choice A) NO CHANGE
A
NO CHANGE
(Choice B) was first used in
B
was first used in
(Choice C) was first using
C
was first using
(Choice D) was first being used in
D
was first being used in