Suppose You Slowly, and at Constant Speed, Lift a Book

Suppose you slowly, and at constant speed, lift a book weighing 12 N from the floor to a shelf 2 m above the floor. Neglect air resistance. While you are lifting, the net force on the book is

A) 12 N directed upward.
B) 12 N directed downward.
C) less than 12 N, by an amount that depends on the speed of lifting.
D) zero.
E) more than 12 N, by an amount that depends on the speed of lifting.