Explanation:

To determine the proper sequence of the sentences P, Q, R, and S, let's analyze each sentence:

- S1 is the beginning of the passage, setting the context or introducing a topic.

- S6 is the conclusion or closing statement, often summarizing or providing final thoughts.

Let's consider the middle sentences and their potential sequence:

- P may introduce a cause or an initial detail.

- Q often follows with additional explanation or consequence.

- R might provide further elaboration or a contrasting point.

- S typically concludes or transitions directly into S6.

Given Options:

1. Option a: Sequence P, Q, R, S

2. Option b: Sequence Q, P, S, R

3. Option c: Sequence R, Q, P, S

4. Option d: Sequence S, R, Q, P

Analysis:

- Identify logical connections that guide the flow of information.

- Look for keywords or cues that indicate cause/effect or sequence.

Considering typical passage structures and logical development:

- Correct Sequence: Q, P, S, R

- Q introduces an initial concept or issue.

- P elaborates on the details or reasons.

- S transitions with concluding thoughts or a summary.

- R provides additional context or a different perspective that leads to S6.

Correct Answer: Option 2: b