Answer:
D. I, II, and III
Step-by-step explanation:
When writing a letter of complaint about a service or product, it is mandatory to mention the faulty issue, the details of the product purchased, the details of the buyer and also the things one have done to try to rectify the problem. One cannot simply just write a letter complaining about the fault and bad service without specifying what type of product it was or what the fault is. Giving information about all these will ensure the timely and easier actions on the part of the company. They can make sure the issues are fixed and there won't be any more complains in the future. Providing full details at the start will help solve the issue quicker.