• Engelberg Rice Huller Mechanism:
• Working Principle: The Engelberg huller consists of a fluted cast-iron cylinder rotating inside a concentric perforated metal mesh screen fitted with an adjustable steel resistance blade (huller knife).
• Milling Action: As rough paddy passes through the restricted clearance, severe grain-to-grain and grain-to-metal friction strips the husk and abrasively rubs away the outer bran layer in a single aggressive operation.
• Limitation: Generates intense frictional heat and shear stress, resulting in high grain breakage rates compared to modern rubber roll shellers.
• Conclusion: Friction (Option 3).

Correct option: (3) Friction