Cache logic attempts to predict which instructions and data in
main (primary) memory will be used by a currently executing
program. It then moves these items to the higher speed cache in
anticipation of the CPU requiring these programs and data. Properly
designed caches can significantly reduce the apparent main memory
access time and thus increase the speed of program execution.
* Answer secondary memory is a slower memory (such as a magnetic
disk) that provides non-volatile storage.
* Real or primary memory is directly addressable by the CPU and is used for the storage of instructions and data associated with the program that is being executed. This memory is usually high-speed, Random Access
Memory (RAM).
* Answer virtual memory uses secondary memory
in conjunction with primary memory to present the CPU with a
larger, apparent address space of the real memory locations.

It would be correct to select the first answer if the world "security" was not in the
question.
Source: TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.

Hackers are classified as a human threat and not a classification by itself.
All the other answers are incorrect. Threats result from a variety of factors, although they are
classified in three types: Natural (e.g., hurricane, tornado, flood and fire), human (e.g. operator
error, sabotage, malicious code) or technological (e.g. equipment failure, software error,
telecommunications network outage, electric power failure).
Reference:
SWANSON, Marianne, & al., National Institute of Standards and Technology (NIST), http://csrc.nist.gov/publications/nistpubs/800-34-rev1/sp800-34-rev1_errata-Nov11-2010.pdf, June 2002 (page 6).

Availability is the opposite of "destruction."
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the
Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 59.