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. Man has existed for about a million years.

P: Science, as a dominant factor in determining the beliefs of educated men, has existed for about 300 years; as a source of economic technique, for about 150 years.

Q: When we consider how recently it has risen to power, we find ourselves forced to believe that we are at the very beginning of its work in transforming human life.

R: In this brief period, it has proved itself an incredibly powerful revolutionary face.

S: He has possessed writing for about 6,000 years, agriculture somewhat longer, but perhaps not much longer.

S6. What are future effects, will be a matter of conjecture, but possibly a study of its effects hitherto may make the conjecture a little less hazardous.