When you play this card, it becomes
If the opponent plays Hit and Run and uses the “Order a unit of your choice” option for lack of Cavalry. When Counterattack is played will it play as: a) Hit and Run if you have cavalry; b) One unit of your choice; or c) One unit in the same section that the card was originally played. I would say ‘a)’ as the Counterattack says copy the card, not the action, but decided it needs clarifying in this instance.
That is correct. Copy the card played with Counterattack, not the action taken. “When you play this card, it becomes a copy of the card your opponent played on his or her last turn. Follow the instructions on the cards as if you were actually playing it...”