Final answer:
The term 'Billings' refers to the total amount of client money that agencies use to purchase media and related activities, encompassing media space and time as well as other associated costs and services.
Step-by-step explanation:
The correct answer to the question is B. Media commissions. Media commissions refer to the amount of client money that agencies spend on media purchases and other equivalent activities. When an agency buys media on behalf of a client, it receives a commission from the media owner. This commission is typically a percentage of the media spend. It is one of the ways that agencies earn money for their services.
The term that refers to the amount of client money that agencies spend on media purchases and other equivalent activities is Billings. Advertising agencies often handle large budgets for their clients, which are used to buy media space and time.
These billings reflect the total amount spent on behalf of the client, which includes not only the media purchases but also associated costs such as production, research, and other related services. This is different from media commissions, retainers, activity fees, or ad traffic compensation, which are specific types of payments or structures for services provided by the agency.