Thanks for the question!
The stem indicates that N, P and R are all selected, and asks us to determine what must be true as a result.
Thanks to the last rule, N must be displayed 5. Additionally, R must be either 1 or 6. This creates two local diagrams:
R __ __ __ N __ | L/M __
__ __ __ __ N R | L/M __
According to the second rule, if P
O/S P S/O (block of 3). Clearly, this limits the placement of the block to positions 2-3-4 in the first solution above. However, P cannot be 3 thanks to the second and fourth rules: S must be adjacent to P, but cannot be either 2 or 4. Since P cannot be 3, the first solution (above) is impossible. Therefore, the second solution is the only possible - validating the correct answer choice (A).
Let me know if this helps!