Describe how glucose and oxygen reach every cell in the body and how waste products leave?

How is the male reproductive system different from other body systems? it isn’t necessary to vital signs. it monitors other body systems, and adjusts if necessary. it transports items from one system to another. it is the only system that produces hormones in the male.

Which of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!