A gateway machine has access to the Internet and is trying to reach a machine on the Internet called cactus.org. Although the gateway machine cannot reach cactus.org， another network across town is able to reach cactus.org. Furthermore， the gateway machine can reach the network across town， but cannot ping the cactus.org. Which of the following tools will best help diagnose the location of the problem？（）

• A、iptrace
• B、netstat
• C、tcpdump
• D、traceroute