The respiratory system is best described as the system which removes wastes from cells and exhales them from the body. the system which delivers oxygen directly to cells and takes away carbon dioxide. the system which provides the ability to burn all nutrients in the cells. the system which delivers oxygen to the bloodstream and takes away carbon dioxide.

Option (4).

Explanation:

Respiratory system may be defined as the system involves in the exchange of gases between the tissue, lungs and the outside environment. The respiratory system involves nose, mouth, larynx, trachea, lungs, brochi, alevoli and alveolar ducts.

The oxygen is inhaled in the body and carbon dioxide is exhaled out from the body.  The oxygen is transferred into the blood stream by binding of oxygen with hemoglobin. The oxygen is diffused in to body due to the partial pressure difference of oxygen and carbon dioxide.

Thus, the correct answer is option (4).

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added