Why is there no option for me to indicate that someone can claim me as a dependant

Yes, you can review your answer to this question under the Personal Info section of TurboTax.

1. Open your return and click the down arrow beside "Personal Info."
2. Click Review/Edit.
3. Click Edit to the right of your name.
4. Scroll down to the line "Another taxpayer can claim me as a dependent on their tax return."
5. Click Yes, if this applies to you.
6. Scroll to the bottom and Continue.