DYD teaches: Single/Not or Happy/Not

One of the things I learnt from watching David D's Mastery Series is something he says about quickly identifying whether a woman is:

A) Single and Happy
B) Single and Unhappy
C) Not Single and Happy
D) Not Single and Unhappy

I think it is a good skill to just quickly pick out where this girl is at so that you know where you can take things with her. To cultivate this skill, David also talks about asking the girl later, after you've tried guessing her situation.