Respuesta :
					                   The missing word would be oxygen. The oxygenated blood will come back to the heart, from the lungs via the pulmonary veins which enter the left atrium
					                
					                
					             Answer:
The answer is oxygen
Step-by-step explanation:
I took the test and got this correct. Here were the options:
capillaries
oxygen
carbon dioxide
waste products
 
			                  