Gertrude Stork's Chocolate Shoppe Normally Employs Four Workers

Gertrude Stork's Chocolate Shoppe normally employs four workers.When the Chocolate Shoppe hired a fifth worker the Shoppe's total output decreased.Therefore,________.

A) the marginal product of the fifth worker is negative
B) the total output of Gertrude Stork's Chocolate Shoppe is negative
C) the average product of the fifth worker is negative
D) the fifth worker should be hired only if he is willing to accept a wage lower than the wage paid to the other four workers