The first readers$-$writers problem $\_\_\_\_.$

Select one:

a$.$

requires that, once a writer is ready, that writer performs its write as soon as possible.

b$.$

is not used to test synchronization primitives.

c$.$

requires that no reader will be kept waiting unless a writer has already obtained permission to use the shared database.

d$.$

requires that no reader will be kept waiting unless a reader has already obtained permission to use the shared database.