It's not optional.
There is a rule that says IF somebody else
CAN claim you as a dependent, you are not allowed to claim your own exemption.
If you have sufficient income (usually more than $6300), you can & should
still file taxes; you just doesn’t get your own $4050 exemption (deduction). In
TurboTax, you indicate that somebody else can claim you as a dependent, at the
personal information section.
Even if you had less, you are allowed to
file if you need to get back income tax withholding. You cannot get back social
security or Medicare tax withholding.
Since you are over 18, you parents can only claim you if you were a full time student OR your income was less than $4050.
For full rules see https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html