The minimum clear cover for R.C.C. columns shall be

Answer: Option A

1. Definition of Clear Cover:
The clear cover is the distance between the outer surface of the reinforcement and the exposed surface of the concrete.

2. Importance of Clear Cover in RCC Columns:
It provides protection to reinforcement against corrosion and fire exposure.
Ensures proper bond strength between concrete and reinforcement.

3. Standard Requirement:
As per IS 456:2000, the minimum clear cover for RCC columns should be the greater of 40 mm or the diameter of the bar used in reinforcement.
This ensures sufficient durability and structural integrity under various environmental conditions.

Conclusion:
The correct answer is Option A: Greater of 40 mm or diameter, as per standard RCC design guidelines.