Directions: In this section, each item consists of six sentences of a passage. The first and sixth sentences are given in the beginning as S1 and S6. The middle four sentences in each have been jumbled up and labelled as P, Q, R and S. You are required to find the proper sequence of the four sentences and mark your response accordingly on the answer sheet.

S1. Ocean acidification is a growing concern for marine ecosystems around the world.

S6. It's imperative that conservation efforts focus on mitigating these changes to protect marine biodiversity.

P. The absorption of CO2 by the world's oceans is causing a decrease in pH levels.

Q. This reduction in pH affects the calcium carbonate structures of many marine organisms.

R. Species such as corals, mollusks, and some species of plankton are among the most affected.

S. The impact on these foundational species can have cascading effects on marine food webs.