The management of a pizzeria is conducting a survey on the quality of its pizza and the service provided by the staff. They asked two of the staff members to wait near the entrance for customers who are leaving and quickly conduct a short interview on their experience at the pizzeria. the staff members did this everyday for one week. in the context of sampling, the customers who were being interviewed represenetda
a. probability sample
b. quota sample
c. convenience sample
d. random sample