IP地址为:192.168.50.70,掩码为:255.255.255.248,则该IP地址所在子网的子网有效IP为()
A.192.168.50.33---192.168.50.39
B.192.168.50.41---192.168.50.50
C.192.168.50.65---192.168.50.70
D.192.168.50.66---192.168.50.75