Which one of the following answers is not a possible state of Amazon CloudWatch Alarm?

Which one of the following answers is not a possible state of Amazon CloudWatch Alarm?
A . INSUFFICIENT_DATA
B . ALARM
C . OK
D . STATUS_CHECK_FAILED

Answer: D

Explanation:

Amazon CloudWatch Alarms have three possible states:

OK: The metric is within the defined threshold

ALARM: The metric is outside of the defined threshold

INSUFFICIENT_DATA: The alarm has just started, the metric is not available, or not enough data is available for the metric to determine the alarm state

Reference: http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/AlarmThatSendsEmail.html