the answer is: D. They tried to drive the French out of the Ohio River valley.
That river valley was connected to the Mississippi river. Which means that any country that control that river would have a strategic location that helped them in delivering their goods to american continent through water routes.
Washington's action heavily damaged the French's economy, so the French army water to retaliate against Washington. In the end, his action lead to a European War between great Britain (who backed Washington) and the French empire.