In the explanation of the high frequency of the use of interrogative sentences, Linguist G.N. Leech (方薇,1997:77) discusses two main functions of interrogative sentences. Viewing from the angle of psychology, interrogative sentences divided the process of information receiving into two phases by first raising a question and then answering it. Thus it turns the passive receiving into active understanding. From the linguistic angle, interrogative sentences decrease the grammatical difficulty, be...