Which of the following benefits does adding Multi-AZ deployment in RDS provide?

Answer options:

A.Multi-AZ deployed database can tolerate an Availability Zone failure.
B.Decrease latencies if app servers accessing the database are in multiple Availability zones.
C.Make database access times faster for all app servers.
D.Make database more available during maintenance tasks.

Answer - A and D
Option A is CORRECT because in Multi-AZ deployment, if an availability zone (AZ) goes down, the automatic failover occurs. The DB instance CNAME gets pointed to the synchronously updated secondary instance in another AZ.
Option B is incorrect because Multi-AZ deployment does not affect the latency of the application`s DB access.
Option C is incorrect because DB access time does not get affected by Multi-AZ deployment.
Option D is CORRECT because, during the maintenance tasks, the DB instance CNAME can point to the second instance in another AZ to carry out the DB tasks. 
Some of the advantages of Multi-AZ rds deployments are given below.
If an Availability Zone failure or DB Instance failure occurs, your availability impact is limited to the time automatic failover takes to complete.
The availability benefits of Multi-AZ deployments also extend to planned maintenance and backups. In the case of system upgrades like OS patching or DB Instance scaling, these operations are applied first on the standby, before the automatic failover. As a result, your availability impact is, again, only the time required for automatic failover to complete.
If a storage volume on your primary fails in a Multi-AZ deployment, Amazon RDS automatically initiates a failover to the up-to-date standby.
For more information on Multi-AZ rds deployments, please visit the link
https://aws.amazon.com/rds/details/multi-az/