Bones are not hard all the way through. What is in the middle of your bones? A. spongy tissue
B. hollow pockets of air
C. blood vessels and muscles

Answer in a couple of paragraphs, 1 or 2 at the most if anything! 20 points + brainliest--> explain what all the systems in your body do to work together < --list of systems needed: circulatory systemrespiratory systemdigestive systemexcretory systemnervous system