Is SPI filtering for packets that are part of ongoing communications usually simple and inexpensive? A. No, simply because if the packet is part of an existing connection in the connection table, the packet is droped, usually without further filtering. B. No, if the packet is part of an existing connection in the connection table, the packet is passed, usually without further filtering. C. Yes, simply because if the packet is part of an existing connection in the connection table, the packet is passed, usually without further filtering. D. Yes, simply because if the packet is part of an existing connecion in the connecion table, the packet is droped, usually without further fiering.