Answer
(a) Two
(b) The weight and a force exerted by my hand.
(c) Yes.
(d) No. The weight is due to the gravitational field of the Earth, not a reaction to the force exerted by my hand.
Work Step by Step
(a), (b) and (c): the weight, $W$ (downward), is the force that acts over the brick due to the gravitational field of the Earth. The force, $F$ (upward), exerted by my hand must be equal in magnitude and in opposite direction to the weight in order to keep the book in rest ($F_{net}=0$). So, there are only two forces acting on the brick.
(d) The weight is due to the gravitational field of the Earth, not a reaction to the force exerted by my hand. If I decide to exert a force greater than the weight, the weight will remain the same. That is: $F\ne W$.
