Let's say as a guy, u can only put ur dick in one hole for the rest of ur life. Which hole?
If you could only put ur dick in one hole (mouth, ass, pussy) for the rest of ur life, which hole would it be? U can fuck different people but u can only use the hole u chooses.
assuming it doesn't override consent requirements (Eg : if she wouldn't usually say yes to anal, she still won't say yes to anal), mouth; since it's the one that will be agreed on the most.
assuming for some reason, the lady will consent to it each time, anal.