Concept:An idiom should be understood by its figurative meaning, not its literal words.Explanation:The phrase "never look a gift horse in the mouth" means one should not criticise or question the value of a gift.Checking a horse's mouth can reveal its age, so doing this to a gift horse would mean ungratefully judging the gift.Therefore, the correct meaning is to avoid evaluating a gift that is received freely.Answer:do not try to evaluate a gift