This is true. Urea carries the bloodstream to your kidneys which then transport waste along with water to form urine.
The lactic acid that is building up in his muscles will eventually cause him to stop exercising. The burning sensation comes from the build up of that lactic acid in his muscles.
Answer:
connective tissue comes in a vast variety of forms, yet they typically have in common 3 characteristic components: cells, large amounts of amorphous ground substance, and protein fibers
