FortiClient provides three distinct antivirus scanning modes to suit different security and performance needs. A 'Quick Scan' checks critical system areas and running processes for active threats. A 'Full Scan' performs an exhaustive check of all files and folders on the endpoint. A 'Custom Scan' allows the user or administrator to specify particular files or folders to be scanned, offering flexibility for targeted checks.

A. Proxy scan is an inspection method used by FortiGate firewalls to scan traffic as it passes through the proxy, not a local endpoint scan type in FortiClient.

D. Flow scan (flow-based inspection) is a high-speed inspection mode used by FortiGate firewalls, which analyzes traffic as it flows, rather than a local endpoint AV scan.

- FortiClient 7.4 Administration Guide, page 101, "Malware Protection": "You can configure FortiClient to run a quick, full, or custom malware scan on the endpoint."