Are we all over this again?
No, it's not a choice. Do you think anybody would actually choose to be gay? It's not just about the sex. That's what straight people think of when they think of queers (which is more often than they'll admit).
You can tell many gay people by their manerisms, even if they're not 'out'. I had a friend in the army, who was never interested in the ladies. 15 years later, he accepted he was gay, & now he's with a partner & happy.
It's got something to do with a certain part of the brain. There have been studies done, but I can't be bothered to go look for them again.