There are four different things shown below
All have one common thing (the ? box) which ties them together
What is it?
Jumbled forms of famous internet domains (such .Com, ,edu, .Org, .mil) - which are tied up through WEB - thanks to Omega Krypton
Hence the thing in the box should be
The ? box is
the letter K
each of the lines of letters anagrams to a word if K is added: DUKE, MILK, MOCK, and GROK.