Just called the IBP and told them about this issue. The guy said that fill-in any of the Master degree from the list and complete the form to submit it. After you take a print out just cut the Master degree section with a pen and verify it by your signature.
Somehow, i didn't liked his method. I know I asked from IBP but it doesn't seems a right approach to fill a wrong option and then cut it.
I am going with your idea.