As a persons ages his or her bones tend to become brittle. This happens as is lost from bone A. Protein
B. Iron
C. Marrow
D. Calcium

D

Explanation: the bones can becomew brittle from not haveing calcium

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

emerald ash borer

the emerald ash borer is a green buprestid or jewel beetle native to north-eastern asia that feeds on ash species. females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years. hope this !