Which definition best matches 'rigid'?

• A. stiff
• B. hard
• C. unyielding or not able to be bent
• D. unable to be changed or modified

Answer: (D)

Rigidity centers on inflexibility—things that don’t easily give or adapt. While a rigid object can be physically stiff or hard, the strongest match for this word in everyday use is the idea of not being able to be changed or modified. That captures both physical and abstract senses: something rigid resists bending, and systems, rules, or attitudes described as rigid resist alteration. The other options describe stiffness or hardness in a physical sense, which is close but doesn’t convey the broader, more general idea of being unable to change. So the definition that states it’s unable to be changed or modified best fits the concept of rigidity.