【正确答案】 Sentence C would be regarded better than the other three. In English, if the sayer and the verbal action are put behind the direct speech, they are more than often treated as part of a whole sentence, which contains all the parts above. Therefore, in the written form, people would rather not capitalize the verbal action such as "said", or the initial letter of the sayer, such as "The professor". In sentence B, the verbal action was separated from the sayer by a relative clause, which makes the sentence fragmentary, especially when the predicative is only a single word.