【单选题】

Questions 17 to 20 are based on the following passage.At the end of the passage you will be given 20 seconds to answer the questions.

Now listen to the passage.
When a consumer finds that his purchase has a fault in it, what is the first thing he should doA．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 stor