Which NTP command configures the router to synchronize its clock to 172.24.54.8?

The ntp server 172.24.54.8 command correctly configures a Cisco router to act as an NTP client and synchronize its clock with the specified NTP server at IP address 172.24.54.8. This is the standard command for pointing a device to an upstream NTP source. ntp master 172.24.54.8 would configure the router itself as an authoritative NTP server, which is not the goal here. ntp peer 172.24.54.8 establishes a peer relationship, allowing both devices to synchronize with each other, which is more complex than simply synchronizing to a server. ntp client 172.24.54.8 is not a valid Cisco IOS command for configuring an NTP client.