ANS:C - 24 bar diameters

To determine the required length of the lap in a compression member, we use the formula provided in the question: Lap length>bar diameter×(Permissible stress in bar)5×(bond stress)Lap length>5×(bond stress)bar diameter×(Permissible stress in bar)​ The formula indicates that the lap length should be greater than a certain multiple of the bar diameter. In this case, we're looking for the lap length that is greater than 24 times the bar diameter. The factor of 24 bar diameters is derived from empirical observations and design practices in structural engineering. It represents a conservative estimate to ensure adequate bond between the reinforcing bars and the concrete in compression members. A lap length of 24 times the bar diameter provides sufficient development length to resist bond stress and prevent premature failure of the connection between the reinforcement and the concrete. Therefore, based on design standards and common practice, the lap length should be greater than 24 times the bar diameter to ensure adequate bond strength in compression members.