单选题 When you use the ping command to send ICMP messages across a network, what's the most common request/reply pair you'll see? (Select one answer choice)

A、 Echo request and Echo reply
B、 ICMP hold and ICMP send
C、 ICMP request and ICMP reply
D、 Echo off and Echo on
E、 None of the above

【正确答案】 A

【答案解析】解析：Explanation: The ICMP protocol uses Echo request and Echo reply with the Ping command. The PING utility is the most commonly used message to verify connectivity to a remote device within the network.