Gertrude Stork's Chocolate Shoppe normally employs 4 workers. When the Chocolate Shoppe hired a 5th worker, the Shoppe's total output decreased. Therefore

A) the marginal product of the 5th worker is negative.
B) the total output of Gertrude Stork's Chocolate Shoppe is negative.
C) the average product of the 5th worker is negative.
D) the 5th worker should be hired only if he is willing to accept a wage lower than the wage paid to the other 4 workers.

Answer: A