<h3>I think it B The group(s) that gets the special treatment.</h3><h3 /><h3>I hope this is correct.</h3><h3 /><h3 /><h3 />
A. 2 S O 2, gas, plus O 2, gas, in equilibrium with 2 S O 3, gas.
Gravity acts to accelerate the ball downward, and air resistance acts in a way to slow the ball along it's instantaneous velocity (no matter which way it's moving air applies a force in the opposite direction)
Endoskeleton- an internal skeleton, such as the bony or cartilaginous skeleton of vertebrates.
Exoskeleton- a rigid external covering for the body in some invertebrates animals, especially Arthropods, providing both support and protection.