Top bars are extended to the projecting parts of the combined footing of two columns L distance apart for a distance of A. 0.1 L from the outer edge of column B. 0.1 L from the centre edge of column C. Half the distance of projection D. One-fourth the distance of projection

The correct answer is: C. Half the distance of projection.

Top bars are extended to the projecting parts of the combined footing of two columns L distance apart for a distance of half the distance of projection. This is done to provide additional support for the footing and to prevent it from cracking.

Option A is incorrect because it is not enough to provide adequate support for the footing. Option B is incorrect because it would not provide any additional support for the footing. Option D is incorrect because it would not be enough to provide adequate support for the footing.