Why Do Many People Entering Sales Never Achieve Competence in Selling

Why do many people entering sales never achieve competence in selling?

A) Because they become discouraged and quit before becoming skillful and successful
B) Because being skillful is a different skill set than being successful
C) Because they receive too much support for sales managers
D) Because they are often too direct and honest in the early stages of the sales process
E) All of the above