Answer:
B.) The colonists had a weapons arsenal in Concord.
Step-by-step explanation:
"On April 18, 1775, British troops march out of Boston on a mission to confiscate the American arsenal at Concord and to capture Patriot leaders Samuel Adams and John Hancock, known to be hiding at Lexington."
Pretty much they were trying to stop a rebellion against the British empire. The battle itself started April 19, 1775 but the day before they marched out to confiscate the colonist's weaponry arsenal to prevent the rebellion.
On April 14, 1775, Gage received instructions from William Legge to disarm the rebels and to imprison the rebellion's leaders (with considerable discretion).