【正确答案】正确答案：These two sentences are different in the sense that the thematic structures are different. The theme of a sentence is often the known information, which the sentence is mainly about. Sentence A provides some information about " his carelessness" , since " his carelessness" serves as the theme. Whereas, Sentence B is a statement about "I" , and from the remainder of the sentence the recipient could know some information about me.

【正确答案】正确答案：In sentence A, "A dagger" serves as the theme, with which the sentence could be seen as an answer of "What did the dagger do?" In sentence B, "The tourist" is treated as the given information, around which the sentence develops; thus, the corresponding question of this sentence as an answer could be "What happened to the tourist?"

【正确答案】正确答案：There are still differences of thematic structures between these two sentences, with the first one about "A hurricane" and the second one about "eight people". What"s more, in sentence A, the verb " kill" emphasizes a direct relationship between the hurricane and the eight people, that is, it is the hurricane that caused the people to die. Whereas, in sentence B, a meaning like above is not entailed.