Where do I place commas in this sentence; Snails barnacles coral and sea urchins produce their rigid parts by combining calcium
and carbonate ions.

Snails, barnacles, coral, and sea urchins produce their rigid parts by combining calcium and carbonate ions.

Snails, barnacles, coral, and sea urchins produce their rigid parts by combining calcium and carbonate ions.

depends on your school

when i was in high school i took ap biology my senior year and it was the hardest one for me because my teacher finished the material within the first month of school and then went on to doing advanced college level it was horrible. but at a nearby school ap biology was one of the easier aps. also, it depends on what you are interested i like math a lot so ap calculus was easier for me than most but i hate history so ap us government was harder for me than most.

the answer is