A continuous beam is supported on three simple supports and carries a uniformly distributed load over its entire span. The bending moment diagram for the beam will have a:

$($a$)$ Positive curvature throughout the span.

$($b$)$ Negative curvature throughout the span.

$($c$)$ Zero curvature at some point within the span.

$($d$)$ Combination of positive and negative curvatures.??$>>>$