What does the museum guide instruct the tourist to remember to do when entering the museum?

Coming from a spanish heritage, i can tell you that is incorrect. the correct way is ella los come (manzanas) todos los dias.

Pedro, josie, y heather fue a la quinceañera de virginia. the question is asking who went to the quinceañera. the person answering the question should answer using the ellos, ellas, and ustedes form if they were not part of that group of people.

Right your are correct

The answer is aquella.