Salesperson: When a salesperson is successful, it is certain that that person has been in sales for at least three years. This is because to succeed as a salesperson, one must first establish a strong client base, and studies have shown that anyone who spends at least three years developing a client base can eventually make a comfortable living in sales. The reasoning in the salesperson's argument is vulnerable to criticism on the grounds that it fails to consider the possibility that ['it takes longer than three years for a salesperson to develop a strong client base', 'a salesperson who has not spent three years developing a client base may not succeed in sales', 'some salespeople require fewer than three years in which to develop a strong client base', 'salespeople who have spent three years developing a client base might not yet be successful in sales']