Object Class for Dynamic role is missing in Manager

Hi All,

I'm trying to create a dynamic role 

However, while trying to add an 'object class' , for eg:'Person', I'm unable to view any drop down option. Instead it can see only "object classes". 

I'm actually new to this tool; I might have missed a trivial point somewhere. I request someone to please guide me here

Thanks!

Regards,

Soumya