The following answers are incorrect.
Symmetric Key. Is incorrect because RSA is a Public Key or a Asymmetric Key cryptographic system and not a Symmetric Key or a Secret Key cryptographic system.
Secret Key. Is incorrect because RSA is a Public Key or a Asymmetric Key cryptographic system and not a Secret Key or a Symmetric Key cryptographic system.
Private Key. Is incorrect because Private Key is just one part if an Asymmetric Key cryptographic system, a Private Key used alone is also called a Symmetric Key cryptographic system.