Which of the following proxies cannot make access decisions on protocol commands?

A.
Application

B.
Packet filtering

C.
Circuit

D.
Stateful

Explanation:
Application and circuit are the only type of proxy-based firewall
solutions listed here; the others do not use proxies. Circuit-level proxy firewalls
make decisions based on header information and not the protocols command structure.
Application-level proxies are the only ones that understand this level of
granularity about the individual protocols.