See that this idiot government has pontificated about the explanation mark!
Children as young as 7 will be marked down for using out of context.
So the latest idiot rules are that it should only be used with complete/proper sentences in which there is a verb and begins with "what" or "who".
The dead hand of Gove seems present!
Takes no account of modern use and context.
What Would You Do in this Position?
Estranged Son and Future Granddaughter