An ERP application is deployed in multiple Availability Zones in a single region. The application uses a MySQL database deployed in EC2. In the event of failure, the RTO must be less than 3 hours, and the RPO is 15 minutes. The customer realizes that data corruption occurred roughly 10 Mins ago. Which DR strategy can be used to achieve this RTO and RPO in the event of this kind of failure?

Answer options:

A.Take 15-minute DB backups stored in Amazon Glacier, with transaction logs stored in Amazon S3 every 5 minutes.
B.Use synchronous database master-standby replication between two Availability Zones.
C.Take hourly DB backups to Amazon S3, with transaction logs stored in S3 every 5 minutes.
D.Take hourly DB backups to an Amazon EC2 instance store volume, with transaction logs stored in Amazon S3 every 5 minutes.

Answer - C
Option A is incorrect because restoring the backups from Amazon Glacier would be slow and will definitely not meet the RTO and RPO. 
Option B is incorrect because you cannot go back to the point in time recovery with the synchronous replication. You will always have the latest data. 
Option C is CORRECT because it takes hourly backups to Amazon S3, restoring the backups quickly. Since the transaction logs are stored in S3 every 5 minutes, it will help restore the application to a state within the RPO of 15 minutes. 
Option D is incorrect because instance store volume is ephemeral. i.e. the data can get lost when the instance is terminated.
Note:
Although Glacier supports expedited retrieval (On-Demand and Provisioned), it is an expensive option and is recommended only for the occasional urgent request for a small number of archives. Having said this (and even if we go with the Glacier as a solution), the option also mentions taking database snapshots every 15 minutes. Now, if you keep taking backups every 15 mins, the database users will face a lot of outages during the backup (due to I/O suspension especially in non-AZ deployment). Also, within 15 minutes, the backup process may not even finish!
As an architect, you need to use the database change (transaction) logs along with the backups to restore your database to a point in time. Since option (c) stores the transaction details up to the last 5 minutes, you can easily restore your database and meet the RPO of 15 minutes. Hence, C is the best choice.