Because the molecules that are being transported is moving against its concentration gradient. in other words, its moving from where its low in concentration to where its high in concentration
=====|>WHAT DO YOU MEAN<|===== :/
The cardiovascular system I think. Hope this helps
Answer:
Explanation:The scientific method is a process used by scientists to study the world around them. ... You can use the scientific method to study a leaf, a dog, an ocean, or the entire Universe. We all have questions about the world. The scientific method is there to test if your answer was correct.