esults of public speaking with aview to reaching certain aims through communication. Domestic scholar HuShuzhong(2002) defines it as "rhetor in Greek means orator, public speaker and rhetoricmeans public speaking". In conclusion, public speaking is the art through which thespeakers present their ideas or conviction to a group of people in an organized, deliberatemanner with the purpose of adding to the knowledge and wisdom of listeners, influencingtheir attitudes or behaviors，or just entertaining them.Not all communication involves speaking, nor can all speaking be considered publicspeaking. Seven characteristics or components define public speaking and set it apart frominformal speaking that we usually engage in. Every message has a source, or a point oforigin. The source of a speech is the speaker. Since speaking is a creative process, andgood speaking is indeed an art form, it is the responsibility of the speaker to determineprecisely what the message should be and how it will be applicable to his particularaudience. The second component is the message itself. If there doesn't exist a subjectmatter, there can be no public speaking, and this is why a speaker should be exposed to therhetorical traditions of his country or culture, so that he might understand how messagesare transmitted effectively and why they are remembered. And messages must betransmitted in some manner. Channel is the third component of public speaking，or meansby which the speech is transmitted. Spoken words are carried by sound waves; facialexpressions, gestures, and movement are carried by light waves. In addition, publicspeaking may occur in person or be delivered over radio or television. The audience is aspecific group of people to whom the speech message is directed. And normally, when aspeech is delivered, audience are those that heard the speech in fact. Feedback is the fifthelement of public speaking. As soon as information is provided to the speaker, he or shecan easily assess the influence of his or her speech on the audience. Noise is anything thatinterferes with communication, and some forms of noise are always present. There are twokinds of noise，external and internal. The final component is known as situation orenvironment. It is the setting in which a speech is presented that affects the expectations ofthe audience, the meaning audience members receive, and their subsequent behavior.
2.2 Reviews on Presupposition
A presupposition is the background belief related to an utterance，which must bemutually known or assumed by both the addresser and the addressee for the utterance to beconsidered and it is a very important concept in pragmatics. As Levinson (2001:167) puts it,“In pragmatics, the literature on presupposition is more than that on almost all the othertopics.,. This topic has been approached from different perspectives by different scholars,and various kinds of relevant theories are delivered. In this part, the historical backgroundof presupposition is reviewed at the beginning, and then semantic presupposition andpragmatic presupposition are studied respectively. Since the present research is to study theapplication of pragmatic presupposition in business conference speeches, thepresupposition theory adopted in this thesis is pragmatically oriented，involving its notionand properties. At last, presupposition triggers are studied in detail. Presupposition is a subject widely studied by linguists nowadays, but actually it wasoriginally studied by philosophers and logicians. In 1892，the presupposition phenomenonwas first proposed by the German mathematician and philosopher Gottlob Frege in hisclassical paper On Sense and Reference ? He held that，“If anything is asserted there isalways an obvious presupposition that the simple or compound proper names used have areference" (Frege, 1892(1952：69)).But Bertrand Russell, a B
