单项选择题Which parameters are valid SCREEN options for combating operating system probes?()
A. syn-fin, syn-flood, and tcp-no-frag
B. syn-fin, port-scan, and tcp-no-flag
C. syn-fin, fin-no-ack, and tcp-no-frag
D. syn-fin, syn-ack-ack-proxy, and tcp-no-frag