Answer: My dentist doesn't believe in taking vitamins, so I don't take them either.
Step-by-step explanation:
The logical fallacy authority occurs when one uses the testimony of a particular person who is in the position of an authority even though the person in question isn't an expert in that particular field.
The sentence that exemplifies the logical fallacy "authority" is "My dentist doesn't believe in taking vitamins, so I don't take them either".
In this case, a dentist is an expert with the teeth and not an expert in the field with regards to the question. Therefore, this is a logical fallacy authority.