Final answer:
Liquid sulfur exhibits an unusual physical property where its viscosity increases with increasing temperature.
Step-by-step explanation:
The unusual physical property that liquid sulfur exhibits from about 113∘C to 230∘C is that its viscosity increases with increasing temperature.
When sulfur is in its liquid state, it begins as a straw-colored liquid with low viscosity. As the temperature rises, the sulfur undergoes structural changes, forming longer chains that tangle with each other. This leads to an increase in viscosity, making the liquid become more thick and difficult to pour.
Therefore, option D. Its viscosity increases with increasing temperature is the correct answer.