A User Has Launched an EBS Backed EC2 Instance in the US-East-1a

Multiple Choice

A user has launched an EBS backed EC2 instance in the US-East-1a region. The user stopped the instance and started it back after 20 days. AWS throws up an 'InsufficientInstanceCapacity' error. What can be the possible reason for this?

A) AWS does not have sufficient capacity in that availability zone
B) AWS zone mapping is changed for that user account
C) There is some issue with the host capacity on which the instance is launched
D) The user account has reached the maximum EC2 instance limit