In this sentence arrangement question on marine biology, the first and last parts are fixed; choose the option that gives the most logical order of the middle parts P, Q, R and S.

Introduction / Context:
This jumbled paragraph question is based on an informative passage about marine biology and the importance of marine life. The opening sentence defines marine biology, and the last sentence talks about the range of organisms it covers. The middle parts describe the roles played by marine life. Your task is to arrange P, Q, R and S so that the paragraph reads logically and smoothly from start to finish.

Given Data / Assumptions:

• Sentence 1: Marine biology is the study of organisms in the ocean.
• Sentence 6: Marine biology covers a great deal, from the microscopic to the huge whales.
• P: At a fundamental level, marine life helps determine the very nature of our planet.
• Q: Marine life is a vast resource.
• R: Shorelines are also shaped and protected by marine life.
• S: Marine organisms contribute significantly to the oxygen cycle.
• Options: PSRQ, QPSR, RPSQ, SPQR.

Concept / Approach:
After the definition in sentence 1, the paragraph should logically move to a general statement about the importance or value of marine life, followed by specific examples of how it affects the planet. Commonly, writers begin with a broad claim like “Marine life is a vast resource”, then explain how it determines the planet's nature, contributes to oxygen and shapes shorelines. This specific-to-more-specific pattern should lead smoothly to the concluding sentence, which again broadens the view to cover the range of marine organisms studied in marine biology.

Step-by-Step Solution:
Step 1: Start with the given sentence 1 defining marine biology. Step 2: Among P, Q, R and S, Q (“Marine life is a vast resource.”) is a natural follow-up, giving a broad claim about the importance of marine life. Step 3: P (“At a fundamental level, marine life helps determine the very nature of our planet.”) deepens this idea by emphasising the planetary-level impact. Step 4: S (“Marine organisms contribute significantly to the oxygen cycle.”) provides a concrete example of how marine life influences the planet. Step 5: R (“Shorelines are also shaped and protected by marine life.”) adds another specific effect, this time on coastal geography. Step 6: After these details, sentence 6 (“Marine biology covers a great deal, from the microscopic to the huge whales.”) summarises the scope again. Step 7: The resulting order is 1 – Q – P – S – R – 6, which matches option QPSR.

Verification / Alternative check:
Read the paragraph with the chosen order: “Marine biology is the study of organisms in the ocean. Marine life is a vast resource. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the oxygen cycle. Shorelines are also shaped and protected by marine life. Marine biology covers a great deal, from the microscopic to the huge whales.” The flow is logical: definition, broad importance, fundamental impact, specific examples (oxygen cycle and shorelines), and then a concluding statement about the wide scope of study.

Why Other Options Are Wrong:
In PSRQ, starting with P after sentence 1 jumps immediately into a somewhat abstract claim without first stating that marine life is a vast resource. RPSQ begins with a detail about shorelines before giving the broader context, making the structure feel disordered. SPQR puts the oxygen cycle before stating that marine life is a vast resource, which weakens the logical build-up of general statement followed by examples. Only QPSR establishes a clear hierarchy: broad claim, fundamental principle and two concrete illustrations.

Common Pitfalls:
Students often choose sequences by superficial connection of similar words rather than by understanding how writers structure paragraphs: definition, general claim, supporting details and conclusion. Another common mistake is ignoring the need for smooth transitions between sentences, such as moving from a global statement about resources to specific environmental roles. To improve at such questions, practice reading short paragraphs in textbooks and identifying how authors move from general to specific ideas.

Final Answer:
The most logical order of the parts is QPSR.