The following six sentences come from a paragraph. The first and the last sentence are given. Choose the order in which the four sentences (PQRS) should appear to complete the paragraph.
S1 - The five-year plans are meant for the nation's economic development.
S6 - The most important is, certainly, failure on the family-planning front.
P - What are the reasons for it?
Q - One way of measuring a nation's development is by finding out how much progress there has been in the fight against poverty.
R - The reasons are many.
S - In India, every five-year plan ends with more people coming under the poverty line.
The correct sequence should be ______.