A private cloud is on-premises so you can deploy physical servers.
A hybrid cloud is a mix of on-premise and public cloud resources. You can deploy physical servers on-premises.
Reference:
https://azure.microsoft.com/en-gb/overview/what-is-hybrid-cloud-computing/

There are different payment options in Azure including pay-as-you-go (PAYG), Enterprise Agreement (EA), and Microsoft Customer Agreement (MCA) accounts.
Your Azure costs are 'per subscription'. You are charged monthly for all resources in a subscription. Therefore, to use different payment options per department, you will need to create a separate subscription per department. You can create multiple subscriptions in a single Azure Active Directory tenant.
Incorrect Answers:
A: A reservation is where you commit to a resource (for example a virtual machine) for one or three years. This gives you a discounted price on the resource for the reservation period. Reservations do not provide a way to use different payment options per department.
C: A resource group is a logical container for Azure resources. You can view the total cost of all the resources in a resource group. However, resource groups do not provide a way to use different payment options per department.
D: A container instance is an Azure resource used to run an application. Container instances do not provide a way to use different payment options per department.
Reference:
https://docs.microsoft.com/en-us/azure/cost-management-billing/manage/create-subscription

Reference:
https://docs.microsoft.com/en-us/azure/cost-management-billing/manage/create-subscription