Probably ET and the last row, as you're the last to board and you have no one behind you breathing - tuck yourself into the corner (window).
But really, as other have said if this kind of thing is make or break for you then I think you're not ready to fly because the risk difference between seats is going to be negligible. The odds of someone carrying the disease being sat in your vicinity in CE are going to be the same for every seat assuming even distribution of passengers.