The correct answer is D) it expands. The volume of flammable and combustible liquids increases when the temperature is increased, as per the principle of thermal expansion. As the temperature rises, the liquid molecules gain more kinetic energy, causing them to move further apart and occupy a larger volume. This principle is a fundamental concept in the study of the behavior of fluids, and it is important for understanding the handling and storage of flammable and combustible liquids on board vessels. The other options are incorrect because: A) the volume does not remain constant if the pressure remains constant, as the volume will expand with increased temperature; B) the volume does not contract, but rather expands; and C) the volume does not remain constant, as it increases with temperature.