Question 4706 Deck General

The correct answer is D) environmental loads. Structural stress levels in a Mobile Offshore Drilling Unit (MODU) are the sum of loading stresses and stresses due to environmental loads, such as waves, wind, and currents. These environmental factors can exert significant forces on the MODU's structure, leading to additional stresses that must be accounted for in the overall structural analysis and design. The other answer choices, such as variable loads, mooring loads, and ballast loading, are also important considerations in MODU design, but they do not directly contribute to the structural stresses in the same way as environmental loads.