How can you check the system uptime in Linux?

The command "uptime" is used in Linux to display how long the system has been running since its last boot, along with the current time, number of users logged in, and the system load averages over the last 1, 5, and 15 minutes. When you execute this command in the terminal, it provides a concise overview of the system's operational duration and its immediate performance status.

The other choices do not exist as standard commands in Linux or serve different functions entirely. For example, "system uptime" is not a recognized command and would result in an error if entered in the terminal. Similarly, "checkuptime" is not a standard operating command in Linux, and "sysinfo" might refer to various information display tools or scripts, but it is not a common command used specifically to check the system uptime. Therefore, "uptime" is the correct and direct command to retrieve the system's uptime information efficiently.