Separation based on surface texture/roughness utilizes: (A) Inclined draper (rough canvass belt conveys rough seeds upward while smooth seeds roll down), (B) Velvet roll separator (velvet fabric hooks rough/hairy seeds while smooth seeds slide down), and (D) Magnetic separator (rough-surfaced weed seeds selectively pick up iron powder and oil slurry and are drawn out by magnets). Spiral separator (C) separates strictly on the basis of particle shape and roundness. Hence (A), (B), and (D) utilize surface texture. Option analysis: (A) Omits magnetic separator. (B) Spiral separator operates on shape, not texture. (C) (A), (B) and (D) only is the correct answer. (D) Omits inclined draper.

Spaced bucket centrifugal discharge elevators are the industry standard for handling free-flowing granular materials like cereal grains, pulses, and oilseeds. The buckets are spaced at intervals along the belt and travel at high belt speed ($1.2\text{ to }2.5\text{ m/s}$), discharging material by centrifugal force as they wrap around the head pulley. Option analysis: (A) Continuous bucket elevators run slow for fragile/lumpy materials. (B) Positive discharge is for wet, sticky, or sluggish materials. (C) Spaced bucket centrifugal discharge is the universal grain handling standard. (D) Continuous positive is used for specialized chemicals/minerals.