Biological principles in scrubbing a calluses during a foot spa

Which element forms the basis of all organic organisms a carbon b oxygen c hydrogen d nitrogen

What happens during the experiment stage of the scientific method

Just a quick question. will give pointswhat is the root word of "blood."it is written in my homework as hemat(o) : blood. so, should i write that the root word as hemat or hemato or hemat(o). i'm really confused.