Dealt with this issue last week. The user had simply clicked "allow notifications" on a site they shouldn't have, so I followed option d to solve.
Adware is software designed to give you ads, your browser is not that. If the ads were pop up windows then it would be symptomatic, but the browser delivers any notification to your action centre. I chose D, as there is still a chance the user has browser notifications for legitimate sites.
(I gave a full scan to be safe, and nothing came up. Understandably these ad notifications do come from dodgy websites, but Comptia's step one to the process is "Investigate and verify malware symptoms" of which browser notifications are not.)