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Answer is Right!
Answer is Wrong!
The correct answer is C. The principal called out the names of the winners.
The other options are incorrect because they do not make sense in the context of the sentence. For example, the principal would not call for the names of the winners, because they are already known. The principal would also not call on the names of the winners, because that would imply that the winners are being asked to answer a question. The principal would also not call at the names of the winners, because that would imply that the winners are being summoned.
The word “out” is used in this sentence to mean “to announce publicly.” The principal is announcing the names of the winners to the entire school.