The sentence with correct capitalization is Nina and Trey visited the museum, so they could see an exhibit about the Colonial Era. Here option A is correct.
In this sentence, proper nouns (Nina, Trey, Colonial Era) are capitalized, as well as the first word of the sentence. Common nouns like "museum" and "exhibit" are not capitalized unless they appear at the beginning of the sentence.
Option B has inconsistent capitalization, with "Exhibit" and "About" being capitalized when they shouldn't be.
Option C has incorrect capitalization of "Museum" and "Colonial," as common nouns and adjectives are not capitalized.
Option D has correct capitalization of proper nouns but incorrectly capitalizes "colonial era." In this context, "colonial era" should not be capitalized. Here option A is correct.