Do porn actors have choice to what kind of porn they make?

What I'm wondering in general is, if the porn actors have the choice to say "no" I dont want to have sex with T-Girls or Gay?
Can a male porn actor say "no" I don't wanna have sex with grannys?
Do girls have the choice to say "no" for lesbian? Or "no" to old men?
Do they get fired if they dont? Is it part of the contract?
Do you hire them for more scenes if they dont do gay or lesbian porn?
Can a male porn actor say "no" I don't wanna have sex with grannys?
Do girls have the choice to say "no" for lesbian? Or "no" to old men?
Do they get fired if they dont? Is it part of the contract?
Do you hire them for more scenes if they dont do gay or lesbian porn?