You have to answer "YES". This is important for granting OCI.
US allows dual citizenship and OCI is granted only for those countries that allow its citizens to have dual citizenship.
Please ref. http://www.indianconsulate.com/PDF_FORMS/ocifamilyapplicationsample.pdf for a completed OCI application form.
For questions 19, 20 you can also attach a separate Word document with details.
Good luck,
V!