Answer:
D. Remote server public key
E. OCSP
Step-by-step explanation:
Options D and E are correct because the above question states that its "verifying that a key is valid". This means that it didn't specify which key. Therefore, it sensible that the application wants to verify the validity of the remote host's key. So, in order to use OCSP to verify the validity of that key, that app actually needs the public key of the remote server.