In each question, the first and the last sentences of the passage are numbered S1 and S6 respectively. The rest of the passage is split into four parts. These four sentences are jumbled. Read the sentences and identify their correct and logical order.

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S1: There is no transportation system in any city that can compare in efficiency with the circulatory system of the body.
P: The larger one goes from the heart to the various other parts of the body.
Q: If you imagine two systems of pipes, one large and one small, both meeting at a central pumping station, you'll have an idea of the circulatory system.
R: These pipes are called arteries, veins and capillaries.
S: The smaller system of pipes goes from the heart to the lungs and back.
S6: Arteries are blood vessels in which blood is going away from the heart.
The Proper sequence should be: