The answer to this is DNA.
Answer:
1A - Respiratory = trachea, lungs... however both arteries and veins move oxygen around the body, and are therefore valid answers
1B - Skeletal = bones
1C - Muscular = muscles
1D - Digestive = stomach, large/small intestine
1E - Circulatory = heart, veins and arteries
2. Cellular respiration is the conversion of sugar into energy the cell uses to function via various chemical reactions. Digestion is an example of this. Stomach acid breaks down food into sugars that cells break down further into energy to keep you alive
3. Bones contain bone marrow deep inside of them which is responsible for the creation of red blood cells. Your lungs can move air all they want but would be useless without red blood cells to take the oxygen to cells and take the CO2 away from them.
