Answer: A retrieval cue is B. is something outside your head in the surrounding environment that is related to the memory you are trying to retrieve.
Explanation: A retrieval cue is a stimuli that helps a person to remember something, such as the name of a person or the title of a song. Therefore, a retrieval cue can help an individual to recover an idea that had been stored in long-term memory for some time and to stop the tip of the tongue phenomena. Most times, these cues are part of the external word, that is to say that they are found outside an individual's head. For example, a sign or a face can work as a retrieval cue.