标点符号的用法一直都是SAT语法考试中的重点之一，考频高，易错题多，为了让同学们高效备考，将分数稳握在手，小编会帮助大家梳理及总结标点符号相关的考点。
今天我们来学习冒号在机考SAT语法考试中的两个考点：
考点一：用冒号连接两个完整句
【常见句式】SVO:SVO.
【使用条件】当第二句话对第一句话进行解释、说明、补充等时，两句话之间可以使用冒号连接。
【例句】He has a goal:he wants to be a teacher.
此处a goal=he wants to be a teacher，因此使用冒号最佳。
【小试牛刀】机考Practice 1-Module 2(H)-20
Researchers studying magnetosensation have determined why some soil-dwelling roundworms in the Southern Hemisphere move in the opposite direction of Earth's magnetic field when searching for ____ in the Northern Hemisphere,the magnetic field points down,into the ground,but in the Southern Hemisphere,it points up,toward the surface and away from worms'food sources.
Which choice completes the text so that it conforms to the conventions of Standard English?
A.food:
B.food,
C.food while
D.food
【正确答案】A
【解题思路】第一句话Researchers have determined why…讲了研究磁感的研究人员已经确定了为什么南半球一些居住在土壤中的蛔虫，在寻找食物的时候，会朝着与地球磁场相反的方向移动。之后是个but连接的两个并列句，in the Northern Hemisphere,SV,but in the Southern Hemisphere,SVO.补充说明了这个研究相关的原因，是因为在南北半球，磁场指向不同。这两个并列句，与之前的第一个完整句之间也需要句子连接，此处用冒号来连接是最佳。
【易错点】这道题CD选项最为干扰，由于没有将整个句子读完或者断句错误，考生凭语感，容易把in the Northern Hemisphere理解为了第一句话的状语，因此以为不需要断开。咱们在解题语法题时，一定要将句子读完整，再进行结构划分，越难的题目，也越需要结合原文大意来考虑。
考点2：冒号连接句子和同位语
【常见句式】SVO:同位语.
【使用条件1】当句末同位语是在补充，解释，展开，列举时，会用冒号引导同位语。
【例句】Many countries are developing ecotourism:a type of tourism designed to mitigate environmental damage.
ecotourism=a type of tourism designed to mitigate environmental damage
此处对ecotourism做了详细解释，用冒号很合适
【例句】I like fruits:apples,grapes,and pears.
这里的apples,grapes,and pears是对fruits的列举，如果我们用了逗号来引出同位语，将会变成I like fruits,apples,grapes,and pears.会被误解为这里是四者并列，引起歧义。因此这种情况，不可以用逗号，需要使用冒号引导同位语。
【小试牛刀】CB官方Boundaries-Hard-5
In a 2016 study,Eastern Washington University psychologist Amani El-Alayli found that,among the study participants who experienced frisson(a physiological response akin to goosebumps or getting the chills)while listening to music,there was one personality trait that they scored particularly ______openness to experience.
Which choice completes the text so that it conforms to the conventions of Standard English?
A.high.On
B.high on;
C.high on
D.high on:
【正确答案】D
【解题思路】首先我们确定这道题的主干是El-Alayli found that there was one personality trait that they scored particularly high on.that之后，there之前，双逗号中间的部分是插入语，可以暂且不看，这样简化后，句子结构会更清晰。openness to experience，这个是对于personality trait的解释说明，因此使用冒号。
【易错点】这道题C选项的干扰性很强，主要是由于同学们对句子结构的划分错误造成的，比如有同学会以为El-Alayli found that there was one personality trait that they scored particularly high on openness to experience.这是一个完整句，世界上one personality trait是定语从句的被修饰语，that they scored particularly high on是从句，把被修饰词代入定语从句，恢复一下就是they scored particularly high on the personality trait.这里已经是完整的，如果openness to experience直接在on后做宾语，那么这个定语从句的that就多余了。
【小试牛刀】2022年5月北美27
Though many animals regularly contribute to bioerosion,Russell and his team brought individual purple urchins from their natural environment into the laboratory and placed each in an enclosure atop one of three rock granite,mudstone,or sandstone(fine and medium grain).
Which choice completes the text so that it conforms to the conventions of Standard English?
A.types
B.types;
C.types,
D.types:
【正确答案】D
【解题思路】第一句话中提到了three rock types，后面具体列举是哪三种岩石类型，因此此处用冒号最佳。
【易错点】这道题C选项有干扰，考生可能会觉得句末同位语常用逗号引导，因此也能用，但是涉及到展开列举，逗号会引起歧义，是不可以用的。
【敲黑板！】请同学们注意，无论是哪个考点，哪种考法，冒号前面一定是个完整句，冒号后可以是句子也可以是词或者短语。
