Answer: C) Sentence 3.
Explanation: extraneous information is a statement that is irrelevant or unrelated to the subject being dealt with. In the given script for a radio advertisement, we can see the description of an event, in the first sentence, the speaker gives the name of the event "The 20th annual Hilton High School Bake Sale," and the day and the place where it will take place "will be held this Saturday at the school auditorium." In the second sentence, we can see the information about what will be sold at the sale, and in the fourth sentence we can see the information about the time of opening and closing. The sentence that has extraneous information is sentence 3.