You use the ping command on your Mac to reach a web server.

The `ping` command tests connectivity by sending ICMP echo requests, while Safari normally accesses websites using HTTP or HTTPS over TCP. A server or firewall can therefore be configured to ignore or block ICMP ping requests while still permitting normal web traffic. Apple documents this same principle with firewall stealth mode, which can prevent responses to probing requests such as ICMP ping while allowing authorized application traffic. This makes option C the intended answer. An expired SSL certificate would normally generate a certificate warning in Safari rather than simply prevent ping responses. SPF records relate to email authentication and have nothing to do with ICMP connectivity. If the Mac firewall blocked all outbound network traffic, Safari would not successfully load the website.

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