Linear arches are structural elements that are curved in shape and are used to support loads such as bridges, roofs, and towers. They are designed to withstand the forces of compression and tension that are transmitted through the arch. The correct answer to the given question is option 'C', which states that a linear arch has an axial thrust.

Explanation:

Axial Thrust:
Axial thrust is the force that acts along the axis of the arch due to the weight of the structure or the loads that are applied to it. This force is responsible for the compression that occurs in the arch, which helps to keep it stable and prevent it from collapsing under the weight of the loads.

Shear Force:
Shear force is the force that acts perpendicular to the axis of the arch and causes it to bend. This force is caused by the loads that are applied to the arch and is responsible for the deformation and stress that occur in the arch.

Bending Moment:
Bending moment is another force that is caused by the loads that are applied to the arch. This force causes the arch to bend and twist, and it is responsible for the bending stress that occurs in the arch.

Conclusion:
In conclusion, a linear arch has an axial thrust, which is responsible for the compression that occurs in the arch. While a linear arch may also experience shear force and bending moment, these forces are not unique to arches and are experienced by other structural elements as well.