Answer – A and B
1. Configuration Changes - AWS Config runs evaluations for the rule when certain types of resources are created, changed, or deleted.
2. Periodic - AWS Config runs evaluations for the rule at a frequency that you choose (for example, every 24 hours).
For more information on AWS config rules, please visit the link:
http://docs.aws.amazon.com/config/latest/developerguide/evaluate-config-rules.html