Answer:
A is the correct answer-Cost-per-impression
Explanation:
Cost-per-impression differs from cost-per-lick since in the latter the advertisement must be clicked for any cost to be charged to the company whose advert is been displayed.
Cost per order is the amount spent on advertising in ensuring that it ends up in sale.
While click-through refers to the proportion of visitors to a web that clicks on the advert placed in there.