Thanks.depends how much you have till the deadline. U.S copy right office is a better option but it takes 6 months for a script to be registered. still the online registration code given to you instantaneously after submission is enough to cover you . WGA is a good option too but they recharge you after 5 years if you still wanna use their services. For a 5 year gap both wga and U.S copyright are solid options. for more than 5 years U.S copyright is better.