how often should you test backup tapes?

For critical servers, how often should you test backup tapes?

A.
Once a week.

B.
Once a month.

C.
Once a quarter.

D.
Once every six months.

Explanation:
Backup tapes for critical servers must be tested at least once a week.
Incorrect
Answers:
B: For all systems other than critical systems, backup tapes should be tested once a month.
C: Backup tapes for critical servers and non-critical servers should be tested more frequently than once a quarter. A full systems restore is usually tested once a quarter.
D: Backup tapes for critical servers and non-critical servers should be tested more frequently than once half yearly.
References:
Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 547-548.