Easy question. Sampling techniques.

[TLEJ]

Identify the sampling technique used to collect the data.
Nursing supervisors are selected using random numbers in order to determine annual salaries.
Choose one answer.
a. Random
b. Stratified
c. Systematic
d. Cluster
e. Convenience

This one is DESTORYING me..

EDIT: Please explain why you got your answer.

[mathman]

Unless this is a trick question, all I know is that random numbers are used for random sampling.