The shearing resistance of a soil is the ability of the soil to resist sliding or shearing along a certain plane. It is an important parameter in geotechnical engineering as it determines the stability of soil slopes, foundations, and retaining structures. The shearing resistance is influenced by various factors such as soil type, moisture content, density, and structure.

a) Structural resistance and Frictional resistance:
The shearing resistance of a soil is constituted by two components - structural resistance and frictional resistance.

1. Structural resistance: This refers to the internal strength of the soil particles and their arrangement. It depends on the bonding between the particles and the overall structure or fabric of the soil. In cohesive soils (such as clay), the particles are closely packed and have strong interparticle forces, resulting in high structural resistance. In granular soils (such as sand), the particles are loosely packed and have weaker interparticle forces, resulting in lower structural resistance.

2. Frictional resistance: This refers to the resistance offered by the soil particles against sliding or shearing due to frictional forces. It depends on the interlocking between the particles and the roughness of their surfaces. The frictional resistance is related to the normal stress acting on the soil plane and the angle of internal friction of the soil. In cohesive soils, the frictional resistance is relatively low compared to the structural resistance. In granular soils, the frictional resistance is the primary component of the shearing resistance.

b) Shearing strength:
Shearing strength is a measure of the maximum shearing resistance of the soil. It is the maximum shear stress that the soil can sustain without failure. The shearing strength is determined through laboratory tests such as direct shear test, triaxial test, or vane shear test. It is an important parameter for designing safe and stable geotechnical structures.

c) All of the above mentioned:
The correct answer is option 'A' - structural resistance and frictional resistance. Both these components contribute to the overall shearing resistance of the soil. The structural resistance is more dominant in cohesive soils, while the frictional resistance is more dominant in granular soils. The shearing strength of the soil is a measure of its overall shearing resistance.

In summary, the shearing resistance of a soil is constituted by the structural resistance and frictional resistance. The structural resistance depends on the internal strength and arrangement of soil particles, while the frictional resistance depends on the interlocking and roughness of the particles' surfaces. The shearing strength is a measure of the maximum shearing resistance of the soil.