Respuesta :
"You should thank the reader and state your expectation of a positive result" is what you should include in the closing paragraph of your letter of complaint, since this is more likely to get you results.
The correct answer is A.
When writing a letter of complaint, it is very important to maintain a calm and peaceful tone. No threats should be made.
On the contrary, at the end of the letter you should thank the reader for its time and respectfully state that you hope to achieve a satisfying and possitive result.