规则
Information that is needed to identify which person or thing you mean is essential and is not separated by commas. "That" introduces essential clauses.
用来确定所指对象的信息是必要信息，不用逗号隔开。that引导必要从句。
✔ 正确： Students who study regularly tend to score higher.
✘ 错误： Students, who study regularly, tend to score higher.
→ 改正： Remove both commas: the clause tells us which students.
技巧: If removing the words changes or confuses the meaning, they are essential: no commas.
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。