Answer
(a) negative
(b) zero
Work Step by Step
(a) We know that as the pendulum moves form point II to point III, it goes in the opposite direction to that of gravity. Thus, the work done on the bob by gravity is negative.
(b) As the bob travels from point II to point III, the tension in the string acts on it in a perpendicular direction. Hence the work done in this case is zero because $W=Fdcos90^{\circ}=Fd(0)=0$
