強調：
強調是一種修辭方式，如前面所說的"倒裝"就是一種重要的強調手段。
此外，還可以借助助詞進行強調，例如：
She did come yesterday; I saw her in the office.
(她昨天確實來了;我在辦公室見到她的。)
本講要討論的主要是"it is ….that…"強調句, 即：將句子中除謂語動詞以外的成分(主語、賓語、狀語等)用"it is ….that…"加以連接，組成強調句，如果是人，也可以用"it is… who…", 例如：
John bought a toy train for his son yesterday.(昨天約翰給他兒子買了輛玩具火車。)
強調主語：It was John who (或that)bought a toy train for his son yesterday.
強調賓語：It was a toy train that John bought for his son yesterday.
強調賓語(或目的)：It was for his son that John bought a toy train yesterday.
強調時間狀語：It was yesterday that John bought a toy train for his son .
學習強調句要注意以下兩點：
不要與主語從句相混淆，例如：
It is well known that light travels in straight lines.
(眾所周至，光以直線傳播。—— 主語從句)
It was not until the early 18th century that the significance of the event was generally realized.
(直到18世紀初，這一事件的意義才為公眾所認識�！獜娬{句)
強調句與主語從句的簡單區(qū)分是：強調句去掉"it is…that…",句子結構依然正確，意思不變，如上句："until the 18th century the significance of the event was not generally realized". 但是主語從句就不行，如上句："well know that light travels in straight line"就不通, 句中 "well know" 變成了無依著的成分。
不要陷入"考試陷阱"，例如：
It was not until 1943 ______ Penicillin was put into clinical use that many fatal diseases were brought under control.
A.that
B.when
C.before
D.after
看到這個題目，考生第一個反應是"強調句"，很快選擇了A，但是再仔細讀一下，句子后面已經有"that"，說明這個題目的考點不在"強調句"上，而是考"定語從句"的"關系副詞"when, 故正確答案是B，A稱為"干擾項".
