Salamanders can regrow entire limbs and regenerate parts of major organs, an ability that relies on their immune systems, research now shows. ... They then wiped out some or all of the macrophage cells to determine whether these cells were essential for regrowing the limbs.
The first three answers I think. I read this a month or two ago for k12. So I'm pretty sure it would be the first three. Hope I could help!
You're right, the answer is caring. :)