冒号（colons）
1、用于独立句子之后，及所引用的单词、短语、句子、引文或清单之前。
Lately, I have had only one thing on my mind: graduation.
Lately, I have had one thing on my mind: graduating from college.
Lately, I have had only one thing on my mind: I can't wait to graduate.
Lately, I have had several things on my mind: papers, grades, and finals.
2、在直接引用清单的动词后无需使用冒号。
The things on my mind are the follwing: papers, grades, and finals.
The things on my mind are papers, grades, and finals.