Alicia is traveling and wants to plug her phone into the charger in her hotel room. What security precaution can she use to ensure that her phone is NOT attacked by a malicious device built into the charger in her room?

USB data blockers are used to ensure that cables can only be used for charging, and not for data transfer. None of the other answers to this question are used for this purpose, and in fact all were made up—USB is a serial bus, circuit breakers are used for power, and HMAC-based one-time password (HOTP) is a type of multifactor token algorithm.