二，拋磚引玉。顧名思義，這種文章開頭絕不會是文章中心。這類文章一般會在開頭引入一個例子（這種例子的典型的特點是有具體時間人物事件）。然后，在通常情況下，對該例子進行轉折，或者負評價（本質上也是轉折，與轉折分開論述是因兩者表現(xiàn)形式不一樣），或者是總結。

（一）轉折的基本標志諸如：however, yet, but的出現(xiàn)一般標志著文章主題的出現(xiàn)。不過，還有一些轉折大家庭里的詞匯也是大家需要留意的，如：despite, still, in fact.或者一些意義上表示轉折的詞如：surprisingly（如99年6月PR那篇文章），today（如2000年12月垃圾回收那篇文章）等等。這些轉折一般出現(xiàn)在第一段末尾或者第二段開頭。轉折在拋磚引玉型文章中最常出現(xiàn)。

（二）其次是負評價，雖然沒有轉折詞，但是對前文進行的否定型的評價一樣意味著文章中心的出現(xiàn)。最典型的一篇文章要算93年6月關于時尚這篇文章的論述了，第一段說了一大堆，第二段開頭：Changing fashions are nothing more than the intentional creation of waste 馬上對時尚做了一個負評價。對整個文章的褒貶定了一個調。把這句話讀懂，大意就可以有個了解了。在做題時甚至是細節(jié)題都可以直接排除一些正評價的選項了。

（三）開頭引一段例子，其后進行總結的文章諸如99年一月英國草蓋屋一文第一段尾出現(xiàn)總結性評價。這類文章中心出現(xiàn)是以therefore, as a result, so, thus, hence等詞匯的出現(xiàn)為標志的。在此不一一贅述 。在做拋磚引玉型文章時也需注意以下一個特點或者叫做難點，即有些文章轉折出現(xiàn)得靠后，這就要求同學們把文章重心的理解放在靠后出現(xiàn)的轉折后面的內容。這種文章有以下幾篇：97年6月份關于洛杉磯大地震（despite出現(xiàn)在第四段首），95年一月英國工作一文（but出現(xiàn)在第三段首），99年6月玩具一文（第三段首出現(xiàn)轉折），02年1月道德下降一文（第三段首出現(xiàn)轉折）02年6月心理壓力一文（第三段首出現(xiàn)轉折）。以97年6月份關于洛杉磯大地震這篇文章為例我們稍作分析。

After the violent earthquake that shook Los Angeles in 1994, earthquake scientists had good news to report: The damage and death toll（死亡人數(shù)）could have been much worse.

More than 60 people died in this earthquake. By comparison, as earthquake of similar intensity that shook America in 1988 claimed 25,000 victims.

Injuries and deaths were relatively less in Los Angeles because the quake occurred at 4:31 a.m. on a holiday, when traffic was light on the city's highways. In addition, changes made to the construction codes in Los Angeles during the last 20 years have strengthened the city's buildings and highways, making them more resistant to quakes.

Despite the good new, civil engineers aren't resting on their successes. Pinned to their drawing boards are blueprints（藍圖）for improved quake-resistant buildings. The new designs should offer even greater security to cities where earthquakes often take place.

In the past, making structures quake-resistant meant firm yet flexible materials, such as steel and wood, that bend without breaking. Later, people tried to lift a building off its foundation, and insert rubber and steel between the building and its foundation to reduce the impact of ground vibrations. The most recent designs give buildings brains as well as concrete and steel supports. Called smart buildings, the structures respond like living organisms to an earthquake's vibrations. When the ground shakes and the building tips forward, the computer would force the building to shift in the opposite direction.

The new smart structures could be very expensive to build. However, they would save many lives and would be less likely to be damaged during earthquakes.

前三段全部在談地震的影響及死亡人數(shù)少的原因，不知道文章中心在哪兒，第四段開頭出現(xiàn)：Despite the good new, civil engineers aren't resting on their successes.緊跟著出現(xiàn)文章主題：Pinned to their drawing boards are blueprints（藍圖）for improved quake-resistant buildings.所以在做主題題時關鍵在與把這一句讀出來。這樣在做最后一題

25. The author's main purpose in writing the passage is to ________.

A) compare the consequences of the earthquakes that occurred in the U.S.

B) encourage civil engineers to make more extensive use of computers

C) outline the history of the development of quake-resistant building materials

D) report new developments in constructing quake-resistant buildings

的時候就不會出錯了。