Which of the following are true regarding System.Threading.ReaderWriteLockSlim ?

a.It is optimized for single processor/core operatons.

b.It is optimized for usage where writes from multiple sources are common

c.A thread which has a read lock on a resource may not acquire a write lock on the same resource.

d.By default , a thread which has a read lock on a resource and attempts to get another  read lock on the same resource will throw an exceptoin.