If the average bending stress is 6 kg/cm2 for M 150 grade concrete, the length of embedment of a bar of diameter d according to I.S. 456 specifications, is A. 28 d B. 38 d C. 48 d D. 58 d

The correct answer is A. 28 d.

The length of embedment of a bar of diameter d according to I.S. 456 specifications is 28 d for M 150 grade concrete. This is because the minimum anchorage length for a bar in M 150 grade concrete is 28 d, as per IS 456:2000. The anchorage length is the length of the bar that must be embedded in the concrete to ensure that the bar can carry the required load.

The other options are incorrect because they are not the minimum anchorage length for a bar in M 150 grade concrete.