What does a high gc current block busy event value indicate?

What does a high gc current block busy event value indicate?

A.
Access to cached data blocks was delayed because they were busy either in the remote or the local cache.

B.
A large number of requested blocks were not cached In any instance.

C.
Asynchronous input/output (I/O) is disabled.

D.
Delay in processing has occurred In the GCS, caused by CPU saturation and would have to be solved by additional CPUs and load-balancing.