✿在TOEFL iBT Reading 考試中每篇閱讀篇章皆會有一至二題之修辭目的題(Rhetorical Purpose)，題型概有下列型式：

Why does the author mention / indicate …..?
Why does the author provide the information that …..
The author mentions ….. in order to ….
What is the purpose of ….. presented by …..

針對此種類題，必須參究該考點詞所在之句中若出現關鍵詞~
如：for example；for instance；  Indeed；that is；in other words….; 相關之指示詞或代名詞等; 再判讀前句以解答。

Savannas typically experience a rather prolonged dry season. One theory behind savanna formation is that wet forest species are unable to withstand the dry season, and thus savanna, rather than rain forest, is favored on the site. Savannas experience an annual rainfall of between 1,000 and 2,000 millimeters, most of it falling in a five- to-eight-month wet season. Though plenty of rain may fall on a savanna during the year, for at least part of the year little does, creating the drought stress ultimately favoring grasses.Such conditions prevail throughout much of northern South America and Cuba, but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern. In these areas, rainfall per month exceeds that in the above definition, so other factors must contribute to savanna formation.

1. In paragraph 2, the author mentions savannas in Central America, Brazil,and the island of Trinidad in order to
(A) argue that these savannas are similar to those in South America and Cuba
(B) point out exceptions to the pattern of savanna formation in areas with drought stress
(C) provide additional examples of savannas in areas with five-to-eight-month wet seasons
(D) indicate areas where savannas are being gradually replaced by rain forests

題目：在第二段中，作者提到中美洲，巴西與島國千里達之草原(savannas)之目的為何?
關鍵：關鍵字詞--- savannas in Central America, Brazil, and the island of Trinidad
原文定位--- 段落第五句, Such conditions prevail throughout much of northern South America and Cuba, but many Central American savannas as well as coastal areas of Brazil and the island of Trinidad do not fit this pattern.

這些條件遍佈盛行在南美洲之北部大多數地區及古巴；然而許多中美洲草原及巴西的海岸地區與千里達島和並不適合此型態。
句子出現such conditions…，因而推衍前句所敘述之條件；Though plenty of rain may fall on a savanna during the year, for at least part of the year little does, creating the drought stress ultimately favoring grasses.

雖然在一年當中草原地區有極豐沛之降雨，然而，一年至少有大半時間都幾乎無雨的，因而造就乾旱壓力最終有利於草原之形成。

Though / Although 皆是表示轉折，後面子句之訊息則為答案。
顯然引述前句之所列之相關條件是不會巴西海岸地區與島國千里達出現，因此答案選擇B，作者之目的用以指出由乾旱壓力所導致草原形成型態之例外。