A simply supported rectangular beam is uniformly loaded and is prestressed. The tendon provided for prestressing should be
(a) Straight, above centroidal axis
(b) Straight, below centroidal axis
(c) parabolic, with convexity upward
(d) Parabolic, with convexity downward
(a) Straight, above centroidal axis
(b) Straight, below centroidal axis
(c) parabolic, with convexity upward
(d) Parabolic, with convexity downward