In this scheme , is confidentiality guaranteed? A sends to B an encrypted file which is encrypted by B's public key. Can you illustrate any variant, still RSA- based but also using symmetric cryptography (no pre-shared keys) and lowering CPU time?
Encryption is about maintaining confidentiality so I daresay that if you encrypt then you maintain confidentiality.
The exam question you quote probably wants you to talk about hybrid encryption (use RSA to encrypt an AES key; use AES to encrypt gigabytes of data). Look it up !