Final answer:
Colonists adopted the symbol to demonstrate unity against British policies during the Revolutionary War, which represents their common cause for independence and not support for other entities or policies.
Step-by-step explanation:
Using Source 1, the statement that best describes why colonists adopted the symbol in the time leading to the Revolutionary War is D. Colonists adopted the symbol to show their unity against British policies. The evidence from various sources illustrates that the Revolution succeeded largely because colonists united in their opposition to Great Britain, despite their differences in social and economic status. This unification was a response to British efforts to consolidate control over the colonies, which incited resistance from colonists seeking to maintain their autonomy and protect their liberties.
Even though the American Revolution divided some colonists, the Patriots, or revolutionaries, used common symbols to show unity against the British. This unity was not a show of support for French efforts, support for British policies, or against creating a new country, as other options suggested. Rather, it demonstrated a cohesive stand against the British system and for American independence.