Answer:
Described as "the shot heard round the world," British soldiers (also called red coats) in April of 1775 and minutemen (the colonists' militia) exchanged gunfire at Lexington and Concord in Massachusetts. This signaled the start of the American Revolution.
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Explanation:
Red Guards, in Chinese history, groups of militant university and high school students formed into paramilitary units as part of the Cultural Revolution (1966–76). These young people often wore green jackets similar to the uniforms of the Chinese army at the time, with red armbands attached to one.
B. Biosphere (not too sure)