Rearrange the following parts of the sentence to form a coherent paragraph about agriculture and climate change in developing and least developed countries. 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 at a time when per capita income will likely have doubled. Q: It may still be vulnerable to climate change for many years to come. R: In developing countries, in contrast, as much as a third of gross national product and half the population currently depend on agriculture. S: Agriculture is practically the only sector of the economy affected directly by climate.

Introduction / Context:
This rearrangement question discusses how agriculture and economies in developing and least developed countries may be affected by climate change. The four parts mention dependence on agriculture, vulnerability, the role of agriculture as the only climate affected sector and a scenario for least developed countries. The challenge is to order these so that they form a logically connected mini paragraph comparing different country groups and highlighting vulnerability.

Given Data / Assumptions:

• R states that in developing countries a large share of gross national product and population depend on agriculture.
• Q remarks that it may still be vulnerable to climate change for many years to come.
• P discusses least developed countries and how a drastic reduction in agricultural productivity would raise the cost of living.
• S says agriculture is practically the only sector of the economy directly affected by climate.
• "It" in Q refers back to agriculture based economies described in R and the subsequent discussion.

Concept / Approach:
For this comparative economic passage:

• Identify which sentence opens the discussion of developing countries; R clearly uses "in contrast", implying earlier context from a larger passage but still forming a reasonable start for this set.
• Follow this with a statement about vulnerability using the pronoun "It", which must refer to agriculture in such economies.
• Then move to the specific case of least developed countries in P, which builds on the general statement.
• Finally, end with S as a general summary that reinforces why agriculture is central when discussing climate change and economic impact.

Although the passage appears to be part of a longer text, we choose the best local ordering among the given options.

Step-by-Step Solution:
Step 1: R introduces the focus on developing countries and quantifies dependence on agriculture, making it a strong starting point within the given set. Step 2: Q follows because "It may still be vulnerable to climate change" refers to the agricultural sector and economies described in R. This sentence comments on that dependence. Step 3: P then shifts the focus to least developed countries, which is a natural next step after discussing developing countries and vulnerability. It describes a possible scenario where reduced agricultural productivity raises living costs. Step 4: S works as a general reinforcing remark about agriculture being practically the only sector directly affected by climate, summarising why the earlier discussion about climate change and agriculture matters. Step 5: The order RQPS therefore develops the argument from dependence, to vulnerability, to concrete consequences, and then to an overall generalisation.

Verification / Alternative check:
When read as RQPS, the paragraph flows sensibly, even though we sense that some earlier context is missing from the original longer passage. Among the given options, PQRS would have "It may still be vulnerable" follow a scenario in least developed countries, which makes the pronoun "It" ambiguous. RPSQ places S last but separates the vulnerability sentence Q from R, weakening the connection between dependence and vulnerability. The "none" option is incorrect because RQPS provides an acceptable coherent sequence.

Why Other Options Are Wrong:

• PQRS: Begins with least developed countries before establishing the general dependence pattern in developing countries, and the pronoun "It" in Q does not clearly refer to any single entity.
• RPSQ: Interrupts the natural connection between R and Q by inserting P, making "It may still be vulnerable" feel less directly tied to the dependence described in R.
• none: This suggests that no arrangement is correct, but RQPS forms a clear, if partial, mini paragraph.

Common Pitfalls:
Candidates may be tempted to choose "none" when the text feels like an extract from a larger passage, but in competitive exams, one of the given orders almost always works best internally. Another pitfall is not carefully tracking the pronoun "It" in Q. If "It" cannot be unambiguously linked to a previous noun, the order is wrong. R immediately before Q gives the cleanest reference to agriculture dependent economies.

Final Answer:
The most coherent order among the given options is RQPS, so the correct option is RQPS.