Purchasing an online ad on a CPA basis means that the advertiser:
A) pays for impressions in 1,000 unit lots.
B) pays a pre-negotiated fee for each click an ad receives.
C) pays only for those users who perform a specific action, such as registering, purchasing, etc.
D) exchanges something of equal value for the ad space.
Answer: C) pays only for those users who perform a specific action, such as registering, purchasing, etc.