What happens when a campaign consistenly meets its average daily budget?

What happens when a campaign consistenly meets its average daily budget?

A) Ads in that campaign will stop showing for the rest of the billing cycle
B) Average cost-per-click (CPC) bids will be lowered
C) Your budget is automatically adjusted
D) Ads in that campaign will show less often than they could

Answer - Ads in that campaign will show less often than they could