【单选题】

{{I}}Questions 11～13 are based on the following talk. You now have 15 seconds to read Questions 11～13.{{/I}} When a consumer finds that his purchase has a fault in it, what is the first thing he should do

A、complain personally to the manager.
B．threaten to take the matter to court.
C．write a firm letter of complaint to the store of purchase.
D．show some written proof of the purchase to the store.