What is wrong with the following description of internal forces is（）
An internal force is an additional interaction between parts of an object caused by an external force
B. The internal forces are continuously distributed throughout the cross section
C. The internal force varies with the external force
D. An internal force is an interaction between particles in an object
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The assumption of deformed solids in material mechanics does not include（）
A. Continuity hypothesis
B. Uniformity hypothesis
C. Isotropic hypothesis
D. Plane hypothesis
In the tensile experiment of low-carbon steel, the stage where the stress remains basically the same while the strain increases significantly is called（）
A. Elastic region
B. Yielding
C. Strain hardening
D. Necking
On the assumption of uniformity, the of a component is assumed to be the same everywhere（）
A. Displacement
B. Stress
C. Strain
D. Modulus of elasticity
When the shear stress exceeds shear proportional limit of the material，which of the following is correct（）
A. The reciprocal theorem of shear stresses is not valid
B. The reciprocal theorem of shear stresses is right
C. Shear hooke’s law still is right
D. Shear deformation is still elastic deformation
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