In the following item, a scientific passage about Frederick Soddy and Ernest Rutherford is jumbled. The passage has six sentences, of which S1 and S6 are fixed as the opening and closing sentences. The middle four sentences labelled P, Q, R and S have been removed and jumbled. Read the passage carefully and choose the option that gives the correct logical sequence of P, Q, R and S between S1 and S6. S1: One of the many young scientists who chose to throw in their lot with Rutherford was an Oxford physical chemist, Frederick Soddy. S6: We now know that Gamma rays are a particularly fierce form of X rays. P: His association with Rutherford lasted only two years, but that was long enough to change the whole face of physics. Q: He was just twenty three. R: They found that thorium changed into a new element, thorium X, and in the process gave off what was apparently a gas and at the same time a third type of ray, which they named after the Greek letter Gamma. S: When he teamed up with Rutherford, they investigated thorium which, as Marie Curie had shown, was radioactive. The proper sequence should be

Introduction / Context:
This jumbled passage narrates the early work of Frederick Soddy with Ernest Rutherford on radioactive thorium and the discovery of Gamma rays. The first sentence introduces Soddy as a young scientist who joined Rutherford, and the last sentence explains what Gamma rays are. The middle sentences describe his age, their collaboration and their discoveries, and must be arranged to form a coherent scientific story.

Given Data / Assumptions:

• S1: Introduces Frederick Soddy as a young Oxford physical chemist who joined Rutherford.
• S6: States that Gamma rays are a very strong form of X rays.
• Q: He was just twenty three.
• S: When he teamed up with Rutherford, they investigated radioactive thorium.
• R: They found that thorium changed into thorium X and emitted a gas and a third type of ray, which they called Gamma.
• P: His association with Rutherford lasted only two years, but it was long enough to change physics.
• We assume that Soddy's age is mentioned soon after his introduction, and that their research and discoveries are detailed before discussing how long the association lasted.

Concept / Approach:
To reconstruct the correct order:

• Place the simple biographical detail about his age immediately after he is introduced.
• Then describe what they did together, starting with the investigation of thorium.
• Next, mention what they discovered during that investigation, including Gamma rays.
• Finally, conclude with the statement about the duration and impact of their association before S6, which explains Gamma rays in a modern perspective.

Chronology and cause and effect are again the main guides.

Step-by-Step Solution:
Step 1: After S1 introduces Soddy, the question “How young was he?” naturally arises. Sentence Q answers that by stating, “He was just twenty three.” So Q directly follows S1. Step 2: After stating his age, it makes sense to describe what he actually did with Rutherford. Sentence S explains that when he teamed up with Rutherford, they investigated thorium, a radioactive element. This gives the context for their joint work. Step 3: Once the investigation is introduced, the passage should describe their findings. Sentence R states that thorium changed into a new element, thorium X, and that a gas and a new type of ray, named Gamma, were emitted. This is the key scientific discovery that leads directly into S6. Step 4: Sentence P comments on the significance of this two year association, saying that it was enough to change the whole face of physics. This reflective remark fits well just before S6, which gives a modern understanding of Gamma rays. Step 5: The resulting sequence is Q S R P between S1 and S6, giving a smooth narrative from introduction and age, to collaboration, to discovery, and then to long term significance.

Verification / Alternative check:
Read the assembled passage with Q S R P inserted. After S1 you immediately learn how young Soddy was, then what he worked on with Rutherford, followed by the specific discovery related to thorium and Gamma rays, and finally a comment on how influential this short collaboration was. S6 then reinforces that Gamma rays are now known to be a very fierce form of X rays. There are no contradictions or unexplained jumps, so the sequence is verified as coherent.

Why Other Options Are Wrong:
P Q S R: Placing P straight after S1 talks about the duration and impact of the association before we even know what their research was or how old Soddy was, making the narrative feel out of order.
Q P S R or Q P R S: These put the commentary about the duration of their association directly after the age statement, delaying the description of the actual research and discoveries and weakening the logical build up to S6.
Only Q S R P correctly arranges the factual details and the evaluative comment in a natural and informative sequence.

Common Pitfalls:
In science based jumbled passages, students sometimes focus on technical terms like “Gamma rays” and jump prematurely to those sentences, ignoring the narrative structure. Another common error is to place reflective or concluding comments like P too early, before the main findings have been described. Always identify which sentences describe events or discoveries, which provide background details, and which offer conclusions or evaluations, and then order them accordingly.

Final Answer:
The correct order is Q S R P, so the correct option is “Q S R P”.