He doesn't like that look. Quite apart from feeling like it's drilling into him, it looks doubtful. And the questions annoys him even more.

'Are you kidding? Delta, I've never been more serious about anyone in my whole life, of course it isn't a fling! Putting aside that flings don't usually last this long, they're usually only about the sex and we're way more than that, that's why we're talking things out to figure out how we can make it all work instead of just saying "see ya" and being done with it as soon as one of us goes off anywhere.' Does Delta really think so little of him? Of them?