What options can channels have to restrict the types of ads that are shown on their channel?
(A) Channels can pick which advertiser can show ads on their channel.
(B) Channels are not able to block the different types of ads that may show up on their channel.
(C) Channels can only block all ads or show all ads.
(D) Channels can block the types of ads that may be inappropriate to the channel, like sensitive or age-appropriate ads or competing ads.