问答题 《复合题被拆开情况》 Sales letters are very important as they are designed to create awareness to the public about a company’s offers, products and services. Sales letters are more effective compared to other means of product advertising such as blogs, newspapers, and magazines. There are basically several ways to write sales letters. It can either be formal or informal, depending on your target market, audience, and the promotion (促销) type. Then, how do you write an effective sales letter to boost (提高) sales? It should be written in an interesting way so as to draw the attention of the reader to your letter’s message. The body of the sales letter can be divided into three paragraphs. The first paragraph should introduce the products or services. The second one should emphasize the strong points of them. And finally, the last paragraph should encourage action.《问题》：What factors can decide whether your sales letter should be formal or informal? The________, and the promotion type.