Aretrieval cue:
(a)-is something inside your head that is related to the memory you are trying to retrieve.
(b)-all of these choices are correct.
(c)-is called the tip-of-the-tongue state.
(d)-is something outside your head in the surrounding environment that is related to the memory you are trying to retrieve.

(a)-is something inside your head that is related to the memory you are trying to retrieve.

Explanation:

                   A retrieval cue is something that is stored in the brain's memory that helps us to remember something when we want to recall.

                  Whenever we make some new memories, we introduce some  information about the situation that triggers to access that memory from the brain.

                  The memory is inside our head that we are able to relate and try to retrieve from certain cues. For example when we meet someone at a place, we try to remember the situation of that place and also what made us introduce ourselves, we try to remember some special character like what type of place it was whether it was at the party or at office or at someone's place.

     So we meet the same person again, we try to remember or recall them better by the help of these cues.

Thus the answer is

(a)-is something inside your head that is related to the memory you are trying to retrieve.

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