It helps keep the heart beating at a steady pace so that it doesn't beat to slow or to fast, it helps prevents heart attacks.
I'm pretty sure its B?
(pls mark this brainliest)
Acidic rain that can deteriorate limestone bases structures
Try this web site. It might have the answer. But you might have to scroll down some. https://quizlet.com/16339858/chapter-34-the-plant-body-flash-cards/