Answer:
animals, oxygen combines with food in the cells to produce energy for daily activity and then gives off carbon. The carbon combines with oxygen to form carbon dioxide (CO2) and is released back into the atmosphere as a waste product when animals breathe and exhale
Answer:
Heres a link to a labeled diagram of the heart. Sorry I was trying to put a picture in but It wouldn't save as a JPEG file
Link:
https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwjpw8LI4vzlAhVMPn0KHWHnCTkQjRx6BAgBEAQ&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FFile%3ADiagram_of_the_human_heart_(cropped).svg&psig=AOvVaw2LsD24TXBtoTcH1kjWCRJC&ust=1574476068782790
The answer that I got is C.
Primary productivity is a term used to describe the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem. There are two aspects of primary productivity. hope this helps!