John has subscribed to a cloud-based service to synchronize data between his smartphone, tablet, and PC. Before allowing the data to be synchronized, this service uses a process in which the cloud service and the client on the smartphone will verify the security of all devices’ security certificates.
What type of security does the cloud-base service employ?
A. Mutual authentication
B. VPN
C. IMAP
D. Tethering

A. Mutual authentication

Explanation:

Mutual Authentication or two way authentication involves two parties in a network connection authenticating each other's digital certificate in order to be assured of the other party's identity.

Since this is as described in the scenario above, the cloud-based service and the devices uses mutual authentication.

just dont use the app.its not a good one,consumes a lot of ur head without any benefits