Crushing terminology check: identify the wrong statement about gape, angle of nip, crushing efficiency, and reduction ratio.

Introduction / Context:
Standard terms in comminution carry precise meanings used in design and performance evaluation. Mixing them up leads to wrong selections and misleading efficiency figures.

Given Data / Assumptions:

• Conventional definitions for gape, nip angle, crushing efficiency, and reduction ratio.
• Comparison asks for the incorrect statement.

Concept / Approach:
Crushing efficiency (in the Rittinger sense) is defined as surface energy created divided by energy supplied to the machine. Because only a tiny fraction of input energy creates new surface, efficiency values are very small. The other listed definitions are standard and correct.

Step-by-Step Solution:
Gape: largest open distance in a jaw crusher → correct.Angle of nip: geometric angle where a particle is just gripped by rolls → correct.Reduction ratio: size_feed,max / size_product,max → correct.Efficiency statement given flips the ratio; it claims energy absorbed by the solid divided by new surface energy, which is not the standard definition.

Verification / Alternative check:
Textbook relations show efficiency = (surface energy created) / (energy input), sometimes referenced to energy absorbed by the solid, which is still in the denominator, not the numerator.

Why Other Options Are Wrong:
(a), (b), (d) align with standard definitions and are not wrong.

Common Pitfalls:
Confusing efficiency definitions from crushing vs. grinding; misinterpreting “energy absorbed by solid” vs. “energy input to machine.”

Final Answer:
Crushing efficiency is the ratio of the energy absorbed by the solid to the surface energy created by crushing.