Parents names dont have surnames. how do i fill out their details in my ds-160 form?

I’m filling my DS - 160 form right now. applying for F1 visa. In the family section, they have asked for father and mother names. In my parents’ passports, they have no surnames. only given names. how do i fill it up in the form? also, my mother is my travel sponsor. how do i fill out her name ? im not allowed to leave the surname blank and she doesnt have a surname as per her passport.

You can write FNU there. Means for Family name unknown.