Circle the correct item. 3 You ...... a teenager when you are aged thirteen to nineteen.

The correct answer is C. The sentence describes a state or condition that is generally true for a person within a certain age range. The present simple tense is used for general truths. 'You' is a second-person pronoun, and the verb 'are' is the correct form of 'to be' for the present simple tense with 'you'.