An administrator chose a shared-tenant model for a cloud deployment.

The shared-tenant model for a cloud deployment, also known as a multi-tenant model, allows multiple customers to use the same resources and infrastructure of the cloud service provider, with each customer's data and applications isolated from one another. This model is often chosen for cost savings, as resources are shared and users only pay for what they use. Therefore, the MOST likely reason that an administrator chose this model is A. Cost savings.