The bending moment at any section of a beam is the algebraic sum of which forces?

The correct understanding of the question involves recognizing that the bending moment at any section of a beam is influenced by various forces acting on it. The bending moment is a measure of the internal moment that develops due to these forces, which can cause the beam to bend.

The bending moment at a section is primarily calculated by considering the effects of forces acting to the left and right of that section. This includes concentrated loads, which are external forces acting at specific points, and distributed loads, which spread over a certain length of the beam. The algebraic sum of these loads gives insight into how they contribute to the bending moment at that section.

While the option mentioning displacement of the section does relate to the deflection of the beam as a whole, it does not specifically address how bending moments are calculated. Displacement is a result rather than a contributing factor to the calculation of the bending moment itself. Hence, understanding the contribution of concentrated and distributed loads is essential in evaluating the bending moment at any given point along the beam, making that the correct answer.