C is the correct answer. There is an understood you as follows: “for once in your life, [you should] try something new and exciting”. ‘For once in your life’ in this sentence is an adjunct and is extra information given to emphasise the strength of the speaker’s feelings.
C. an understood you ;
The subject of the sentence "For once in your life, try something new and exciting" is implied as "you," making option C the correct answer. This is typical in imperative sentences where the subject is understood rather than stated. Therefore, the answer is (C) an understood you.
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