Some agents are classified as "servants" while others are classified as "independent contractors." Which of the following best describes the main difference between these two kinds of agents?
A. Servants are paid whereas independent contractors are not.
B. Servants have to pay income tax whereas independent contractors do not
C. Independent contractors are paid whereas servants are not
D. Independent contractors have to pay income tax whereas servants do not
E. Servants are subject to the direct control of the principal whereas independent contractors are not