The correct tense of the underlined verb in the sentence "The stripes represented the first thirteen colonies of the United States" is:
C. represent
The original sentence is in the past tense, but if you're looking for the present tense form that matches the intended meaning in a more general context, "represent" would be the appropriate choice. However, if you were analyzing the sentence as it is written, the verb "represented" is already correct for that context. But given the options and the question's context, "represent" is the present tense form that could be considered correct.