Size reduction of the __________ can be suitably done by ball mills, crushing rolls and rod mills.

The correct answer is:

👉 B. Non-metallic ores

Explanation:
Ball mills, crushing rolls, and rod mills are commonly used for size reduction of non-metallic ores such as quartz, feldspar, phosphate, mica, and asbestos.

These mills are well suited for materials that are softer or less abrasive compared to metalliferous ores.

Metalliferous ores usually require more robust crushing and grinding equipment (e.g., autogenous or SAG mills).

Summary:
A. Metalliferous ores – Typically need heavier, more robust equipment.

B. Non-metallic ores – Best suited for ball mills, rod mills, and crushing rolls.

C. Basic slags – May require specific handling but not typically processed by all these mills.

D. Asbestos & mica – Asbestos processing requires special care, though mica falls under non-metallic ores.

Final answer: B. Non-metallic ores