The correct inference that can be made from Madame Jourdain's aside, "He scratches him where it itches," is:
A. It suggests that Monsieur Jourdain’s vanity and insecurity make him vulnerable to Dorante’s flattery.
This interpretation highlights how Dorante is likely appealing to Monsieur Jourdain’s vanity and insecurities, thereby suggesting that he is manipulating him through flattery.