Exercise is beneficial to your heart. A 22-year study was conducted by doctors in California. They found that people who work at physical jobs experience fewer heart attacks than other people. These active people work all the time at moderate speeds, their daily routine gives them an adequate amount of exercise and helps them stay in shape.
“Exercise is beneficial”這是毫無疑義的。但主題句中如不加上“to your heart”來加以 control 和 limit,那就流于空泛。
因此,緊緊把握主題句中controlling idea的導向和制約作用,是短文寫作成功關鍵之一。
2.推展句
2.1 主要推展句
主要推展句（major supporting statement）的主要特點是：圍繞段落主題句展開的每一個推展句本身都不要求作進一步的說明或證明,句與句之間的關系是相互獨立又是互相連接的。
例1：（主題句） There are several factors affecting climate. （推展句1）One factor is the mount of sunlight received. （推展句2）Altitude, or the height above sea level, also determines climate. （推展句3）The oceans have an effect on the climate of adjacent land. （推展句4）In addition, climate is influenced by the general circulation of the atmosphere.
主題句指出影響氣候的幾個因素。然后用四個擴展句說明四種因素。第一種是太陽光的接收量,第二種是海拔高度,第三句和第四句分別是海洋和大氣環(huán)流因素。
2.2 次要推展句
次要推展句（minor supporting statement）是指對主要推展句作進一步的事實分析和舉例說明。它從屬于某一個或某幾個推展句。
例2：（主題句）I don't teach because teaching is easy for me. （主要推展句1）Teaching is the most difficult of the various ways I have attempted to earn my living： mechanic, carpenter, writer. （主要推展句2）For me, teaching is a red-eye, sweaty-palm, sinking-stomach profession. （次要推展句1）Red-eye, because I never feel ready to teach no matter how late I stay up preparing. （次要推展句2）Sweaty-palm, because I'm always nervous before I enter the classroom, sure that I will be found out for the fool that I am. （次要推展句3）Sinking-stomach, because I leave the classroom an hour later convinced that I was even more boring than usual.
從屬于主要推展句2的三個次要推展句起著解釋說明作用,分別解釋red-eye, sweaty-palm, sinking-stomach的含義,這就更加形象生動地證明了 “teaching is not easy” 這個主題。
2.3 主要推展句與次要推展句的關系
主要推展句與次要推展句的關系（relation）基本可以遵循下面的“三部分”（three-part）規(guī)則。
1〕每個主要推展句都應該是對主題句中表示主要思想的關鍵詞的直接、明確的說明。
2〕每個次要推展句都應該說明它的主要推展句。
3〕含有討論說明或分析的問題通常既要有主要推展素材,又要有次要推展素材。
“Exercise is beneficial”這是毫無疑義的。但主題句中如不加上“to your heart”來加以 control 和 limit,那就流于空泛。
因此,緊緊把握主題句中controlling idea的導向和制約作用,是短文寫作成功關鍵之一。
2.推展句
2.1 主要推展句
主要推展句（major supporting statement）的主要特點是：圍繞段落主題句展開的每一個推展句本身都不要求作進一步的說明或證明,句與句之間的關系是相互獨立又是互相連接的。
例1：（主題句） There are several factors affecting climate. （推展句1）One factor is the mount of sunlight received. （推展句2）Altitude, or the height above sea level, also determines climate. （推展句3）The oceans have an effect on the climate of adjacent land. （推展句4）In addition, climate is influenced by the general circulation of the atmosphere.
主題句指出影響氣候的幾個因素。然后用四個擴展句說明四種因素。第一種是太陽光的接收量,第二種是海拔高度,第三句和第四句分別是海洋和大氣環(huán)流因素。
2.2 次要推展句
次要推展句（minor supporting statement）是指對主要推展句作進一步的事實分析和舉例說明。它從屬于某一個或某幾個推展句。
例2：（主題句）I don't teach because teaching is easy for me. （主要推展句1）Teaching is the most difficult of the various ways I have attempted to earn my living： mechanic, carpenter, writer. （主要推展句2）For me, teaching is a red-eye, sweaty-palm, sinking-stomach profession. （次要推展句1）Red-eye, because I never feel ready to teach no matter how late I stay up preparing. （次要推展句2）Sweaty-palm, because I'm always nervous before I enter the classroom, sure that I will be found out for the fool that I am. （次要推展句3）Sinking-stomach, because I leave the classroom an hour later convinced that I was even more boring than usual.
從屬于主要推展句2的三個次要推展句起著解釋說明作用,分別解釋red-eye, sweaty-palm, sinking-stomach的含義,這就更加形象生動地證明了 “teaching is not easy” 這個主題。
2.3 主要推展句與次要推展句的關系
主要推展句與次要推展句的關系（relation）基本可以遵循下面的“三部分”（three-part）規(guī)則。
1〕每個主要推展句都應該是對主題句中表示主要思想的關鍵詞的直接、明確的說明。
2〕每個次要推展句都應該說明它的主要推展句。
3〕含有討論說明或分析的問題通常既要有主要推展素材,又要有次要推展素材。