ANS:A - Sewage sludge

Among the options provided, the substance that best fits the description of an ideal plastic material is sewage sludge.

Explanation:

1. Ideal Plastic Substance:
   • An ideal plastic material exhibits no deformation when stressed up to its yield stress point. This means it behaves like a solid until a critical stress (yield stress) is reached.
2. Behavior Beyond Yield Stress:
   • Beyond the yield stress, an ideal plastic material behaves like a Newtonian fluid, meaning its viscosity remains constant regardless of the applied stress. This behavior is characteristic of materials like mud, sewage sludge, or certain types of clay.
3. Options Analysis:
   • Sewage sludge: Sewage sludge typically exhibits ideal plastic behavior because it can withstand a certain stress (yield stress) without deforming (like a solid) and then flows like a fluid once this stress threshold is exceeded.
   • Rubber latex: Rubber latex is elastic and does not behave like an ideal plastic material.
   • Blood: Blood is a non-Newtonian fluid, exhibiting complex viscosity changes under different stresses, not consistent with ideal plastic behavior.
   • Sugar solution: Sugar solutions typically behave as Newtonian fluids, with viscosity dependent on temperature and concentration, not exhibiting plastic behavior.

Conclusion: