A supermarket manager wants to poll customers coming to shop with regards to a proposed change to the bakery.The manager selects the first person they see enter the store, then every 30th customer after that one until they have interviewed 40 customers. This type of sampling is known as

A.

voluntary response.

B.

stratified random sampling.

C.

systematic random sampling.

D.

cluster sampling.

E.

simple random sampling.