An end user calls the company’s IT service desk to report an inability to open encrypted emails on a mobile device. Which of the following BEST represents a
possible cause?

A.
A valid certificate suitable for S/MIME is not installed.

B.
Emails received by the user lack suitable digital signatures.

C.
SSL/TLS certificates stored on the device are expired.

D.
The sender did not have the addressee’s public certificate.