听力原文：F: We are honoured that you have come to see us, Mr. Mitchell. M: Thank you, Madam Ii. We're pleased to be here and appreciate your willingness to arrange this meeting on such a short notice. F: You have indicated that you would like to explore the possibility of an agency relationship with Sinochem with the intent of developing a market for some of our products in your country and perhaps in Canada as well. M: Yea, that is certainly our current thinking. F: Perhaps before we begin any detailed discussions, I should give you some idea of the scope of activities of Sinochem. M: The name 'Sinochem' is well known to us, but we would like a little more information about your company. I should tell you that your branch in the U. S. has already informed us that Expert Division No. 4 is responsible for dyestuffs and pigments. F: Sinochem was established in 1950 and since that time has grown to become one of the largest companies in China, specializing in imports and exports of chemical products. As a result, it has gained a great deal of experience (in foreign trade) and has many foreign clients. The primary products we handle are crude oil and oil products, plastic, rubber, fertilizer and pesticides, ss well as dyestuffs and pigments. You expressed a particular interest in our various dyestuffs as well as our pigments. M: I glanced through these catalogues and noted the wide variety of products Sinochem offers. F: You mentioned earlier that you would like to concentrate on dyes for cotton, silk, and linen materials. M: Yes, that is what we intend to do. F: In that case, you may wish to take a look at our sulfur and reactive dyes. Sulfur dyes have been around for a very long time and have been used for dying sturdy work clothing from early history. You will note that the variety of eolours in which this sulfur dye is available is somewhat limited, particularly in the bright hues. They are also cheaper than the reactive dyes. M: I gather then that the reactive dyes are used primarily for fine cottons, silk, and linen. F: That is correct. M: I particularly lire the wide variety of bright eolours available in reactive dyes. Is there any difference in price from one colour to another? F: Yes, there certainly is. The most expensive is the colour, identified as Brilliant Blue KNR, under Sinochem Code No.9607. A cheaper colour dye would ha, for example, Brilliant Red K-JBP the most economical of course is Black. M: I assume of course that not much expertise is needed in producing black. ?You will hear part of a business negotiation between Mr. Mitchell and Madam Li. ?For each question 23—30, mark one letter A, B or C for the correct answer. ?You will hear the recording twice. 21. What is the purpose of Mr. Mitchell's visit?