Final answer:
The command 'uname -r' is used to display the Unix kernel release information, which includes the version. Other 'uname' options perform different functions, such as displaying the network hostname or kernel build version.
Step-by-step explanation:
The command used to display the Unix version is 'uname -r'. The 'uname' command stands for 'unix name' and the '-r' flag specifies that you want to see the kernel release information, which includes details about the version. The other options you mentioned have different uses:
uname -n displays the network node hostname.
uname -t is not a commonly used option; it might not provide any output.
uname -v shows the kernel version (which is the version and date of the kernel build, not the distribution version).
To know the specific distribution version on a Linux system, you might need to use special commands or files like 'cat /etc/os-release' or 'lsb_release -a' depending on the distribution.