That question appears in My Info. Click edit by your name. Make sure you know the correct answer if you plan to say no one else can claim you.
If you can be claimed as a dependent and you answer the question in My Info incorrectly, here is what happens if you e-file first: Your Social Security number goes into the IRS system as having been used. When your parents try to e-file, their e-file is rejected and they will find it impossible to e-file their own tax return. Then they will have to print, sign and mail their return and wait for months for it to be processed. You, meanwhile, will have to file an amended tax return on a special form called a 1040X, which also takes months for the IRS to process. So make sure you know the correct answer to "Can anyone claim you as a dependent on their tax return?"