问题：

[问答题]Passage 6Coherence　　Coherence determines whether a speech is logical and thus makes sense. The speaker must make (31)______ that his utterances and paragraphs are presented in a logical sequence so that his thoughts and ideas are readily acceptable. A speech may be compared (32)______ a freight train. The locomotive is the thematic statement in a speech that gives the train (speech) its direction. Each car is an utterance in a paragraph or a paragraph in a speech that must follow the (33)______ of the train, for it must go where the locomotive goes. It is couplings that hold the cars together, ensuring that all the cars will arrive at same destination as the locomotive. (34)______ the same way, a speaker must supply the links between the utterances and paragraphs to give his listeners a directional signal to indicate (35)______ is to follow and how it (36)______ to what is preceded.　　Since transmitting ideas orally requires attention to the perceived coherence of speaker’s message, the audience do not have the luxury of going back (37)______ his points as they do in reading an essay; nor do they have punctuations that help them (38)______ one idea from another. Hence, speakers use signposts in the form of carefully worded phrases and sentences to help listeners (39)______ the movement of ideas within a speech and perceive the overall message structure. Summaries are (40)______ signposts in ensuring that listeners are able to see the overall structure: preliminary and final summaries are especially helpful in laying our or pulling together the major divisions of the speech. 确定