A and B are both good defenses to her claims. Coral reefs are vital for the survival of marine ecosystems and the other is a major health risk of using sunscreen containing the chemical.
Ok, so I'm going to try my best to answer this.
My best guess would be how he said that he was able to see his answer through whoever he is talking to, then lose it again. He understood and got something, then lost it's understanding. I sincerely hope this helps.. I'm sorry I'm not very good at explaining. ^^;
Answer:
She should remind him of the rules for discussion and ask him to provide supporting information.