How to determine the distribution of Ubuntu

Ubuntu 16.04 (the 5th item in the list in the question) is codenamed xenial. You can verify this by opening the terminal and running the following command:

lsb_release -c

If the operating system is 16.04 the results of the above command will be:

Codename:   xenial

Ubuntu 16.04 LTS is code named Xenial Xerus (https://wiki.ubuntu.com/XenialXerus)

The full list of releases can be seen at https://wiki.ubuntu.com/Releases, providing links to end of standard support (or LTS EOL), or ESM support if available.

Without parsing anything, use -r and -c flag to get releases and codename respectively.

$ lsb_release -rc
Release:    16.04
Codename:   xenial