The correct answer is 3.
A Class C address default mask is 255.255.255.0; this indicates 8 bits of host. For 9 LANs, 4 subnet bits are required (resulting in a possible 16 LAN subnets). The remaining 4 host bits can address 14 hosts, which is enough to cover the required 12 hosts. Therefore the last octet of the required subnet mask is 11110000; the subnet mask is 255.255.255.240.
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