A company has three accounts under consolidated billing. "Production" is the payer account, and "Development" and "Staging" are the linked accounts and they have the reserved instances sharing enabled between them. The development account has purchased three reserved instances with instance type of m4.large in Availability Zone us-east-1a. However, no instance is running on the development account, but has five m4.large instances running in the staging account and Availability Zone 1a. Who can receive the benefit of the reserved instance pricing? Choose the correct answer from the options below.

Answer options:

A.All the instances in all the accounts running the m4.large will receive the pricing even if there is only one reserved instance purchase.
B.No account will receive the reservation pricing because the reservation was purchased on the development account, and no instances that match the reservation are running in the development account.
C.The reserved instance pricing will be applied to three m4.large instances in the staging account because the staging account runs an instance that matches the reserved instance type.
D.Only the primary account (the consolidated billing primary account) will receive the discounted pricing if the instance is running in the primary billing account.

Answer – C
Option A is incorrect because the benefit of reserved instance pricing will apply to any three EC2 instances across all the accounts in the Consolidated Billing group. Since the staging account - which is part of the "account family" - has 5 EC2 instances running, only 3 of those will receive the reserved pricing benefit.
Option B is incorrect because even though no EC2 instances are running in the development account, the instances running in the staging account will still receive the reservation pricing benefit since it is part of the Consolidated Billing group.
Option C is CORRECT because the reserved instance pricing will be applied to three of the m4.large instances in the staging account as they are part of the Consolidated Billing group. This needs Reserved Instance sharing to be enabled at the account.
Option D is incorrect because the reserved Consolidated Billing advantage is applied to all the accounts linked to the primary account, not just the primary account.
More information on Consolidated Billing Group
For more information on consolidating billing, please visit the below links-
http://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/consolidated-billing.html
https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/consolidatedbilling-other.html