I haven’t read this passage but if I did and it made sense, I would say (D) Since He’s showing attention towards other people with his eyes and desire, and wants to become better at art like other men. (I tried)
I would say Jane Austen implored the girl to marry only for love in a logical way so that if she really truly loved the man and knew that was the case after examining herself and her feelings carefully, then she should feel that it was a good decision to make and carry through with it.