Final answer:
The ad group level takes priority over the campaign level in targeting a campaign. The correct option is B.
Step-by-step explanation:
The level that will take priority when both campaign-level and ad group-level targeting are applied to a campaign in online advertising is the ad group level. This means that the targeting set at the ad group level will override the targeting set at the campaign level.
For example, if Arlo sets a specific target audience at the campaign level but then sets a different target audience for a specific ad group within that campaign, the targeting at the ad group level will be used for that particular ad group's ads instead of the targeting at the campaign level.
Therefore, the ad group level takes precedence over the campaign level when both are used in targeting a campaign.