A company is planning to set up an Azure account. Can they purchase multiple Azure subscriptions and associate all subscriptions to a single Azure AD Tenant?

Answer options:

A.Yes
B.No

Answer – A 
Yes, you can have multiple subscriptions against a single AD tenant, as shown below in the Microsoft documentation. 

https://docs.microsoft.com/en-us/office365/enterprise/subscriptions-licenses-accounts-and-tenants-for-microsoft-cloud-offerings/