Assertion (A): Ductile materials exhibit a large plastic...

Ductile materials, by definition, can undergo significant plastic deformation (permanent change in shape) before they break. This means Assertion (A) is true. Young's modulus, however, is a measure of a material's stiffness or resistance to elastic deformation. A high Young's modulus indicates a stiff material, not necessarily a ductile one that undergoes large plastic deformation. Ductility is related to a material's ability to yield and deform plastically, which isn't directly measured by Young's modulus alone. Therefore, Reason (R) is false.