Correct option is (b) shear effects caused by eccentric load on a bolt group
Easy explanation: When bolt groups are subjected to shear and moment in shear plane, the load that is eccentric is eccentric with respect to centroid of bolt group can be replaced with a force acting through the centroid of bolt group and a moment (Magnitude = Pe). Both the moment and the force result in shear effects in the bolts of the group and is called as eccentric shear.