**Shear in a Simply Supported Beam**

In a simply supported beam, the shear force is the internal force that causes a structure to resist the external forces applied to it. It is a result of the external loads acting on the beam and the reactions at the supports. The shear force varies along the length of the beam and can be determined by analyzing the equilibrium of forces at any particular section.

**Sinking of a Support in a Simply Supported Beam**

When one of the supports of a simply supported beam sinks, it causes a change in the support conditions and affects the distribution of forces within the beam. The sinking of a support introduces a discontinuity in the beam, leading to changes in the shear force and bending moment at different sections.

**Effect of Sinking Support on Shear**

The effect of sinking of one support on the shear in a simply supported beam can be understood by considering two cases:

**Case 1: Sinking of Support at Midspan**
If one of the supports sinks at the midspan of the beam, it creates a hinge-like condition where the beam is no longer fully supported in the middle. This results in the formation of two separate beams, each with its own reactions and shear forces.

1. The original beam is divided into two segments: the left segment and the right segment.
2. The left segment will have a clockwise moment and a downward reaction at the sinking support, causing a positive shear force.
3. The right segment will have an anticlockwise moment and an upward reaction at the sinking support, causing a negative shear force.
4. Therefore, the sinking of one support at midspan results in two shear forces with opposite signs.

**Case 2: Sinking of Support at One End**
If one of the supports sinks at one end of the beam, it creates an overhanging condition where the beam is no longer fully supported at that end. This introduces additional forces and moments at the sinking support.

1. The original beam is divided into two segments: the supported segment and the overhanging segment.
2. The supported segment will have a downward reaction at the remaining support, causing a positive shear force.
3. The overhanging segment will have a downward force at the sinking support, causing a negative shear force.
4. Therefore, the sinking of one support at one end results in two shear forces with opposite signs.

**Conclusion**
In conclusion, the shear caused by the sinking of one of the supports in a simply supported beam depends on the location of the sinking support. If the support sinks at midspan, it results in two shear forces with opposite signs. If the support sinks at one end, it also results in two shear forces with opposite signs. Therefore, the correct answer to the given question is option (3) Two.