When discussing semaphores first, we tried to avoid the spin$-$lock in the acquire $($sem$\_$wait$)$ function by blocking the calling process. But then when implementing acquire$/$sem$\_$wait and release$/$sem$\_$post, the operations on the shared variable within the these functions become the critical section and we said that they can now be protected using a spin$-$lock. Why is it OK to use the spin$-$lock when implementing semaphore operations while we were trying to avoid in the first place when discussing in the context of applications?

A$.$ The CS code in acquire$/$sem$\_$wait and release$/$sem$-$post is not application specific.

B$.$ The CS code in acquire$/$sem$\_$wait and release$/$sem$-$post is executed in the kernel.

C$.$ The CS code in acquire$/$sem$\_$wait and release$/$sem$-$post is too short

D$.$ The CS code in acquire$/$sem$-$wait and release$/$sem$-$post is more important