What risk arises if powers of entry are not used lawfully?

Answer: A — They could be trespassing.

Entering property without the proper legal authority is trespass. Powers of entry exist only when you have the right statutory basis and, often, notice or other safeguards. If you bypass that and enter premises unlawfully, you invade someone’s property rights, which is a civil or criminal wrong in itself. That makes trespass the direct risk of using powers of entry unlawfully, and it can lead to legal action or disciplinary consequences for the officer. The other outcomes listed aren’t the immediate consequence of unlawful entry: breach of the peace relates to disorder during policing, assault involves using unlawful force against a person, and issues about evidence status aren’t the core risk of entering without authority.