How do cost-per-click (CPC) ads compete with cost-per-thousand impressions (CPM) ads on the Display Network?
A. Ads using CPC bids are not allowed to compete on the Display Network
B. CPM bids are effectively converted to CPC bids
C. CPC bids are effectively converted to CPM bids
D. CPC and CPM bids only compete against bids of the same type
