The word that contains a capitalization error is "Because".
There is a capitalization error because the "b" in "because" should not be capitalized. Although the speaker tag ("said Mr. Thompson") has been added in the middle of the sentence, there is only one sentence. "Because admission is free on that day" is not a second sentence; therefore, the first letter ("b") should not be capitalized. On the other hand, "Tuesday" and "Mr." have been correctly capitalized and the "m" in "museum" must not be a capital letter.
