Which of the following are valid statements about Amazon S3? (Select TWO)

Answer options:

A.S3 provides strong read-after-write consistency ONLY for PUTs.
B.S3 provides eventual consistency for PUTs or DELETES.
C.S3 provides strong read-after-write consistency for PUTs and DELETEs.
D.S3 does not support object locking for concurrent writers.
E.Atomic updates across keys are possible.

Answer: C and D
Options A and B are incorrect because both of them are outdated features of Amazon S3.
Option C is CORRECT because Amazon S3 provides strong read-after-write consistency for PUTs and DELETEs of objects in your Amazon S3 bucket in all AWS Regions. This applies to both writes to new objects as well as PUTs that overwrite existing objects and DELETEs. 
Option D is CORRECT because Amazon S3 does not support object locking for concurrent writers. If two PUT requests are simultaneously made to the same key, the request with the latest timestamp wins. If this is an issue, you will need to build an object-locking mechanism into your application.
Option E is incorrect because atomic updates across keys are not possible. For example, if you PUT to an existing key from one thread and perform a GET on the same key from a second thread concurrently, you will get either the old data or the new data, but never partial or corrupt data.
Reference:
https://docs.aws.amazon.com/AmazonS3/latest/userguide/Welcome.html#ConsistencyModel