规则
A single dash can introduce an explanation or emphasis at the end of a sentence, like a colon. A pair of dashes sets off extra information in the middle.
单个破折号可在句末像冒号一样引出解释或强调；一对破折号用于隔开句中的附加信息。
✔ 正确： The result surprised everyone—even the researchers.
✘ 错误： The result surprised—everyone even the researchers.
→ 改正： Place the dash after the complete sentence "The result surprised everyone".
技巧: A single dash works like a colon: what comes before it must be a complete sentence.
练习：10题
Which choice completes the text so that it conforms to the conventions of Standard English?
由AUSLEX原创的讲解和题目，并非College Board官方资料。SAT是College Board的商标。