Final answer:
The sentence that changes the tone is 'C. Everyone knows Friday night shows are totally dead.' due to its conversational and informal style.
Step-by-step explanation:
The sentence that marks a change from the formal tone of the rest of the passage is C. Everyone knows Friday night shows are totally dead. This sentence uses a conversational and informal phrase "totally dead" which contrasts with the formal and professional tone of the rest of the passage. The other sentences, such as A. She won an Emmy for her guest spot on the show., B. Hayek not only produced the series, but she also guest-starred as a magazine editor., and D. Ugly Betty has won numerous other awards for the show and its actors., all maintain a formal and factual style appropriate for discussing the history and achievements of a television series.