From his vantage point, Erik doesn't need to watch Charles closely to monitor his body language. He does anyway. A bittersweet indulgence he can't linger too long on, or Charles will pick up the conflicting emotions as clearly as he does the actual thoughts Erik is trying to communicate.

I'm trying to figure out what they're asking. The phrasing is unclear. He looks at it again. It's this part here: "...whether engaged in the act of penetrative or oral sex..." Those aren't two different things.