Which is the next stage of detection in an AdWords accont, if Googles automatic filtering system does not successfully remove all potentially invalid clicks?

Which is the next stage of detection in an AdWords accont, if Googles automatic filtering system does not successfully remove all potentially invalid clicks?

A) Advertiser reports suspicious activity in the account
B) Alert from the AdSense team about publisher suspension
C) Third-party analysis of advertisers web server logs data
D) Proactive offline analysis by the Google Ad Traffic Quality Team