ANS:A - tension

The bolt is subjected to tension when the nut is tightened by putting the washer beneath it. Explanation: When a nut is tightened onto a bolt, the applied torque creates a clamping force that holds the joint together. This clamping force generates tension in the bolt, pulling it axially. The tension in the bolt is what allows it to resist external forces and maintain the integrity of the joint. The washer beneath the nut serves to distribute the clamping force more evenly and reduce the risk of damage to the surfaces being clamped. However, the presence of the washer does not change the primary mode of loading experienced by the bolt, which is tension. Therefore, when the nut is tightened by putting the washer beneath it, the bolt experiences tension as the primary mode of loading.