What 2 types of structures do serous membranes line and cover

A serous membrane is an epithelial membrane formed of mesodermally derived epithelium called the mesothelium that is backed by connective tissue. These membranes line cavities that do not reveal to the outside, and they cover the organs located within those cavities. Serous membranes have two layers:  

An external layer that lines the body cavity called parietal.An internal layer that includes internal organs called visceral.  

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.

D) better spellers i would think