Final answer:
In a best-fit placement policy with splitting and immediate coalescing, the block header of p11 will be updated with the new size after the execution of free(p9).
Step-by-step explanation:
In a best-fit placement policy with splitting and immediate coalescing, the block header of p11 will be updated with the new size after the execution of free(p9).
This means that the block header of p11 will be modified to reflect its new size after the memory block previously allocated to p9 is freed.
Therefore, the correct answer is C. Updated with the new size.