In reinforced concrete footing on soil, the minimum thickness at edge should not be less than A. 100 mm B. 150 mm C. 200 mm D. 250 mm

The correct answer is: C. 200 mm.

The minimum thickness of a reinforced concrete footing on soil is 200 mm. This is to ensure that the footing is strong enough to support the load of the structure above it. The footing must also be wide enough to distribute the load evenly over the soil. The width of the footing is typically determined by the load of the structure and the type of soil.

Option A is incorrect because 100 mm is not a sufficient thickness for a reinforced concrete footing on soil. Option B is incorrect because 150 mm is not a sufficient thickness for a reinforced concrete footing on soil. Option D is incorrect because 250 mm is not a typical thickness for a reinforced concrete footing on soil.