What act declared that the colonies were in rebellion and forbade trade between the colonies and Britain?

The Prohibitory Act is the correct answer because this act, passed in 1775 by the British Parliament, officially declared the American colonies to be in rebellion against British authority. It denied the colonies the right to trade and effectively blockaded them, further severing economic ties with Britain. This act was a response to the growing revolutionary sentiments and actions in the colonies, including the Continental Congress's decision to support military resistance against British forces.

The Intolerable Acts were a series of punitive measures taken following the Boston Tea Party, aimed at controlling colonial resistance, but they did not specifically declare the colonies in rebellion nor initiate trade bans. The Navigation Acts were earlier laws focused on regulating colonial trade with the intent of maximizing revenue for Britain, rather than a declaration of rebellion. The Stamp Act, also preceding the Prohibitory Act, imposed taxes on printed materials in the colonies, which was a significant source of tension but did not address the issues of rebellion or trade restrictions in the way the Prohibitory Act did.