Which statement holds true for the term cost$-$per$-$click?

It refers to the ad rates quoted in cost$-$per$-$million impressions.

It refers to the number of users who clicked an ad divided by the number of times the ad was delivered.

It refers to the ad rates quoted in cost$-$per$-$thousand impressions.

It refers to the amount of money an advertiser pays for each click on their ad$.$

It refers to the cost associated with the storage and bandwidth to deliver a website once it is clicked on$.$