In RHEL, which command is used to check system memory usage?

The command used to check system memory usage in RHEL is "free." This command provides a straightforward and comprehensive overview of the system's memory status, including total memory, used and free memory, shared memory, buffers, and cached memory. By executing the command with the option -m, you can display the memory usage in megabytes, which often makes it easier to read and understand at a glance.

The other options do not represent valid commands in the context of checking memory usage on RHEL. "memory," "memusage," and "raminfo" are not standard utilities available in the Linux command-line environment for monitoring memory statistics. Hence, they do not provide the functionality required to check system memory usage, making "free" the correct and most effective choice for this purpose.