Powdery materials can be guarded against caking tendency on storage by

The correct answer is: A. Providing irregular grain size

Explanation:
Caking in powdery materials occurs when individual particles stick together during storage due to:

Moisture absorption

Pressure

Temperature changes

Particle surface properties

Why irregular grain size helps:
Irregular and varied particle sizes reduce the uniformity of packing.

This leads to fewer contact points between particles.

It increases void spaces, lowering the chances of moisture bridging and reducing cohesion.

Hence, caking tendency is minimized.

Option Analysis:
A. Providing irregular grain size ✅
→ Helps prevent caking by reducing particle contact and improving flow.

B. Providing minimum percentage of voids ❌
→ Increases contact between particles, promoting caking.

C. Having maximum possible points of contact ❌
→ Directly increases caking tendency.

D. None of these ❌
→ Incorrect since A is a valid preventive measure.

✅ Final Answer: A. Providing irregular grain size