To accurately determine the tone of the first sentence in the passage from “How to Keep Conspiracy Theories from Ruining Your Time with Family," I would need to see the specific sentence in question. However, based on the options given, you can evaluate the tone by considering the choice of words and the overall message conveyed in that sentence.
If the focus is on concern about the impact of conspiracy theories on family time, "worried" could be the appropriate tone. If it expresses unexpectedness, "surprised" might fit. "Assertive" would suggest a confident, firm expression, while "encouraging" would indicate a positive, uplifting approach.
If you can provide the first sentence, I will be able to offer a more definitive answer!