Concept:Mud wallowing in pigs is mainly a way of cooling the body because pigs do not sweat effectively.
Explanation:Pigs possess very few functional sweat glands, so they are unable to cool themselves efficiently by perspiration.
In hot weather, their body temperature can rise quickly and cause discomfort.
When a pig coats itself with muddy water, the moisture evaporates slowly, helping to cool the skin.
The cooler mud also absorbs and carries away heat from the body by conduction.
Thus, wallowing helps a pig maintain a normal internal temperature and prevents overheating.
Answer:D. lower their body temperature