This is a cell, which is the basic unit of all life. all organs in human bodies are made of cells and require oxygen to survive. which two systems work together to deliver oxygen to cells throughout the body?
a) skeletal and endocrine
b) digestive and endocrine
c) skeletal and respiratory
d) respiratory and cardiovascular

First answer marked as brainiest which is the correct equation describing the first law of thermodynamics? a) when the internal energy of a system changes, it equals the amount of heat added plus the work done. b) when work is done by the piston, it is equal to the heat added plus the change in internal energy of the system. c) when heat is added to the system, it is equal to the amount of work done by the piston plus the change in internal energy of the system.