Explanation:

RPSQ is the best sequence for the above jumbles.
R: In developing countries, in contrast, as much as a third of GNP and half the population currently depends on agriculture.
P: In the least-developed countries, if agricultural productivity were drastically reduced by climate change, the cost of living would rise by one or two percent, and at a time when per capita income will likely have doubled.
S: Agriculture is practically the only sector of the economy affected by climate.
Q: It may still be vulnerable to climate change for many years to come.