Which of the following is not true regarding expiration dates of certificates?
a. Certificates may be issued for a week.
b. Certificates are issued only at yearly intervals.
c. Certificates may be issued for 20 years.
d. Certificates must always have an expiration date.
Answer: B
Digital certificates contain a field indicating the date to which the certificate is valid. This date is mandatory, and the validity period can vary from a short period of time up to a number of years; therefore, answers A, C, and D are incorrect.