Rearrange the parts of the sentence in correct order.

P: But the achievements of science have not come to man as a ripe apple falls in the lap of a man sitting under an apple tree.

Q: Science is not just the result of observation and experience.

R: It is, on the other hand , the result of centuries of hard work done by man, even at the risk of his own life or health.

S: There is no doubt that science has been the greatest boon to man so far.