If the cost-per-thousand impressions (CPM) option is not available for a campaign, the most likely reason is that the campaign:

If the cost-per-thousand impressions (CPM) option is not available for a campaign, the most likely reason is that the campaign:
A) is only opted into the Google Display Network.
B) is only opted into Google search and the Search Network.
C) has never used CPM pricing before.
D) has used CPM pricing before.

Answer: B