C, its too rigid compared to the other answers, as long as you conversate you are improving
The Respiratory System brings oxygen into the blood; it is the responsibility of the Circulatory System to transport it, with nutrients from digestion, to cells of the body.
The Circulatory System is three-fold: the blood carrying the substances, the vessels in which blood flows, and the heart which pumps it around in a circle-like movement and back (hence the term 'circulatory').
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Your answer is 3 number may be
