B. Dot diagrams are used to represent outer electrons.
Answer: respiration
Explanation: It's when the oxygen chemically reacts with sugar inside the cells to release energy. This produces the gas carbon dioxide, which the body needs to get rid of and some water.
Answer:
answer is b
it allows specific substances to cross through it
The cardiovascular system has three main functions:
transport of oxygen, carbon dioxide and nutrients.
clotting of open wounds.
regulation of body temperature.