In the following question, there are six sentences marked S1, S6,...

In the following question, there are six sentences marked S1, S6, P, Q, R, S. The positions of S1 and S6 are fixed. You are required to choose one of the four alternatives which would be the most logical sequence of the sentence in the passage. S1: A force exists between everybody in the universe. P: Normally it is very small but when one of the bodies is a planet, like Earth, the force is considerable. Q: It has been investigated by many scientists including Galileo and Newton. R: Everything on or near the surface of the earth is attracted by the mass of the earth. S: This gravitational force depends on the mass of the bodies involved. S6: The greater the mass, the greater the earth's force of attraction on it. We can call this force of attraction gravity.