Which of these is an optional feature，requiring the purchase of a separate license after 30 days？（）

A. heuristic scanning cannot detect new malware with an unknown signature
B. heuristic scanning requires a separate license key
C. heuristic scanning increases the probability of false positives
D. heuristic scanning increases the probability of false negatives

A. whenever you have an upstream proxy
B. whenever you intend to deploy the L4TM in blocking mode
C. whenever you want to enable the WSA proxy
D. whenever you have a separate management VLAN orsubnetwork