It is relatively easy to spot a gerund, given that it looks like a verb + ing. Having that in mind, the gerund here is drinking from the tap. This gerund acts as the subject of the sentence, which you can easily determine by asking the question What is perfectly safe?, and the answer will be Drinking from the tap - that's how you know it is the subject.
So, the correct answer is drinking from the tap/subject.
C. For is the preposition
Answer:
Not entirely certain, sorry
A. Because she dresses and acts differently depending on where the is
