A．showing the fault of it to the producerB．saying firml……

When a consumer finds that something he or she bought is faulty or in some other way does not live up to what the producer says for it, the first step is to present the warranty, or any other records that might help, at the store of buying. In most cases, this action will produce results. However, if it does not, there are various means the consumer may use to gain satisfaction.
A simple and common method used by many consumers is to complain directly to the store manager. In general, the "higher up" the consumer takes his or her complaint, the faster he or she can expect it to be settled. In such a case, it is usually settled in the consumer’s favour taking it as true that he or she has a just right.
Consumers should complain in person whenever possible, but if they cannot get to the place of buying, it is acceptable to phone or write the complaint in a letter.
Complaining is usually most effective when it is done politely but firmly and especially when the consumer can show clearly what is wrong with what was bought in question. If this cannot be done, the consumer will succeed best by presenting specific information as to what is wrong, rather than by making general statements. For example, "The left speaker does not work at all and the sound coming out of the right one is unclear" is better than "This stereo does not work. "
The store manager may advise the consumer to write to the producer, if so, the consumer should do this, setting the complaint as politely and as firmly as possible. But if a polite complaint does not achieve the expected result, the consumer can go a step further. He or she can threaten to take the seller to court or report the seller to a public organization responsible for protecting consumers rights.
The most effective complaint about what was bought can be made by ______.

A．showing the fault of it to the producer
B．saying firmly it is of poor quality
C．asking politely to change it
D．explaining exactly what is wrong with it