Final answer:
Companies can purchase Premier support plans only if they have an Enterprise Agreement (EA) with Microsoft. These plans provide a higher level of service for large enterprise customers, including personalized support.
Step-by-step explanation:
A company can purchase a Premier support plan under specific conditions. The correct answer is c) Only if the company has an Enterprise Agreement (EA). Premier support plans are advanced support offerings that are available to large enterprise customers who have an EA with Microsoft. These plans are not included in all Azure subscriptions and are separate from regular support plans. They are not exclusive to pay-as-you-go subscriptions and are indeed available to companies, providing them with a higher level of service, including faster response times and access to a wider range of Microsoft resources and experts.