Which describes the meaning of the phrase "the shot heard round the world"?

a.
the shots fired during the boston massacre set off the spark of a revolution that would not be stopped.

b.
the battle at lexington started a revolution that brought the new united states to the world scene.

c.
the battle at breed's hill proved to the world that the united states would win the american revolution.

d.
the violence in new york told the world that americans could fight as well as british soldiers.