Which of the following is the procedure for Coki (or Coki's browser) to verify that the sender is in fact Mala (and not an imposter)?

use Mala's public key to decrypt the digital signature of the file

use the CA's public key to decrypt the digital signature of the file

use the CA's public key to decrypt the CA signature within the digital certificate

this check cannot be performed...there is no way to verify Mala's identity from these transmissions