What are two possible causes for this?

The Global Cache Block Access Latency chart shows high elapsed times. What are two possible
causes for this?

A.
badly written SQL statements

B.
storage network bottlenecks

C.
a large number of requested blocks not cached in any instance

D.
slow or faulty interconnect

Explanation:
About Global Cache Block Access Latency Chart
If the Global Cache Block Access Latency chart shows high latencies (high elapsed times), then
this can be caused by any of the following:
A high number of requests caused by SQL statements that are not tuned.
A large number of processes in the queue waiting for the CPU, or scheduling delays.
Slow, busy, or faulty interconnects. In these cases, check your network connection for dropped

packets, retransmittals, or cyclic redundancy check (CRC) errors.
Oracle Database 2 Day + Real Application Clusters Guide
11g Release 2 (11.2)