在准备SAT文法考试时，很多同学都会发现一个小小的标点符号——逗号，竟然成了让人头疼的大问题。尽管我们每天写作文、写作业都在用逗号，但在考试中，逗号的使用规则却让人觉得有些陌生，甚至有些容易出错。
上期我们说了SAT考试中经常出现的一些逗号的错误用法，今天我们来讨论一下逗号的正确用法，进一步帮助同学们选出这类题目正确的选项。其实，一个小小的逗号，想要正确使用的难度还是不小的，有很多微小的细节一定要注意。
A逗号用于分隔列举的项目
、当题目中需要列举三个或以上的项目时，每个项目后面必须有一个逗号。但是要注意，在and之前的逗号不是必须的，可以有也可以没有。
✔ 正确用法：
The open-storage display brings over 900 vintage World's Fair souvenirs out of attics, desk drawers, shoeboxes, and museum archives for visitors to view.
The open-storage display brings over 900 vintage World's Fair souvenirs out of attics, desk drawers, shoeboxes and museum archives for visitors to view.
同时要注意，在and之后不可以使用逗号。
✘错误用法：
The museum's open-storage display brings over 900 vintage World's Fair souvenirs out of attics, desk drawers, shoeboxes, and, museumarchives for visitors to view.
The museum's open-storage display brings over 900 vintage World's Fair souvenirs
out of attics, desk drawers, shoeboxes and, museumarchives for visitors to view.
另外还要注意，当and后面跟着插入语时，又必须使用逗号了。
✔ 正确用法：
Deserts are found on every continent, including Antarctica. They are often the site of unusual rock formations and, in some cases, amazing archaeological finds.
这里的in some cases就是一个non-essential的成分，此时and后必须使用逗号隔开。
有点复杂了？还有更复杂的：当列举的项目是长短语，或者内部含有逗号时，可以使用分号进行分隔。然而，逗号和分号不能混合使用。
✘错误用法：
Among Marie Curie's achievements were the development of the theory of radioactivity;the invention of techniques for isolating radioactiveisotopes,and the discovery of the elements polonium and radium.
✔ 正确用法：
Among Marie Curie's achievements were the development of the theory of radioactivity;the invention of techniques for isolating radioactive isotopes;and the discovery of the elements polonium and radium.
这里的第一个分号用于分隔列举居里夫人的第一个和第二个成就；第二个分号则是第二个成就和第三个之间的分隔。错误示例当中混用了逗号和分号的分隔。
B
两个顺序可以颠倒的或可以由and分开的形容词
之间应当使用逗号
也就是说，当形容词的顺序不影响语义时，应使用逗号将它们分开。
✔正确用法：
One of the Queens Museum's recent exhibits featured works by contemporary artists from Japan, Taiwan, and Ireland, offering patrons the chance to see a kind of innovative, passionateart that larger museums often ignore.
One of the Queens Museum's recent exhibits featured works by contemporary artists from Japan, Taiwan, and Ireland, offering patrons the chance to see a kind of passionate, innovativeart that larger museums often ignore.
或者，我们可以尝试在形容词之间加上单词"and"。如果它们被and分开后仍然有意义，那么应使用逗号。
C
在引导性词语和短语之后，应当使用逗号
比如：in fact, moreover, as a result…
✔正确用法：
At first,it looked as if the storm was going to miss us by a few hundred miles.
Nevertheless,Armstrong persisted and became an extraordinary musician.
Desserts were traditionally characterized by their sweetness. However,bakers are now creating ones that feature intriguing blends of sweet and savory.
注意到，这些引导性词语和短语都是副词性的；需要强调的是，像although和because这样的从属连词不能这样使用逗号。
✘错误用法：
Desserts were traditionally characterized by their sweetness. Although,bakers are now creating ones that feature intriguing blends of sweet and savory.
虽然是小小不起眼的逗号，但说不定就成为那关键的那几分！所以只要把细节把握住，高分就百密无一疏~
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