What can be the possible reason for this?

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

Explanation:
When the user gets an ‘InsufficientInstanceCapacity’ error while launching or starting an EC2
instance, it
means that AWS does not currently have enough available capacity to service the user request. If
the user is requesting a large number of instances, there might not be enough server capacity to
host them. The user can either try again later, by specifying a smaller number of instances or
changing the availability zone if launching a fresh instance.