Difficult Points(难点) 1.a killer drug(致病的药物)。这里killer是名词,起定语作用。本文中有很多词组是由“名词(起定语作用)+名词”构成的,如narcotics agent, China White, skin cancer. the AIDS epidemic等。2.在现代英语科技文章中,常出现由几个诃构成的词组起定语作用,放在被说明的名词之前,如本文中的any greater-than-normal occurence, a larger-than-normal number, a case-control study等。这种起定语作用的词组,可以由各种词性的单词组合而成,各单词之间加连字符。3.第二段第一句里的falling ill with diarrhea是现在分词短语,修饰people。动词fall常与形容词(或名词)连用,此时fall意为“成为,变得”,如:fall ill(生病),fall asleep(睡着),fall prey to AIDS(成为艾滋病的牺牲者)。4.isn’t necessarily译为“不一定是,未必是”。necessarily是necessary的 Difficult Points 1.a killer drug. Here killer is a noun, a attributive role. Many phrases in this article consist of “nouns (attributives) + nouns” such as narcotics agent, China White, skin cancer. The AIDS epidemic and others. 2. In modern English science and technology articles, it is often found that a phrase consisting of a few hales serves as a attributive effect, preceded by the spelled pronouns, as any greater-than-normal occurence, a larger-than-normal number, a case-control study and so on. This phrase can play a role of phrases, can be composed of various parts of the word combination of words, hyphenation between. 3. The falling ill with diarrhea in the first sentence of the second paragraph is the current participle phrase that modifies people. The verb fall is often used in conjunction with an adjective (or noun), in which case fall means “becoming, becoming”, such as fall ill, falling asleep, falling prey to AIDS. 4.isn’t-essential translated as “not necessarily, not necessarily.” It is necessary