The correct answer is A) hogging with tensile stress on main deck. When a vessel has a midships engine room and the cargo is concentrated in the end holds, the vessel's weight distribution is uneven, with more weight at the ends. This causes the vessel to hog, meaning the center of the vessel bends upwards. As a result, the main deck experiences tensile stress, as the deck is being pulled apart. The other options are incorrect because: B) would indicate sagging, not hogging; C) would indicate sagging with compressive stress on the main deck; and D) would indicate sagging, not hogging, with tensile stress on the main deck.