If your campaign, ad group, or asset group does not have an ad schedule, the ad will serve based on the last schedule you set.

The selected answer option, False, is correct because if a campaign, ad group, or asset group does not have an ad schedule, the ad will not automatically serve based on the last schedule you set. Instead, it will serve continuously, without any time restrictions, meaning it will be eligible to be shown at any time throughout the day or week. An ad schedule needs to be explicitly defined in order to control the specific days and times when the ads are shown. Without such a schedule in place, the ads will be served without any time limitations.