Columbia unit

例句：

1. 1. The Columbia unit is a popular choice for students who want to learn more about American history.
   哥伦比亚单元是那些希望了解更多美国历史的学生的一个受欢迎选择。
2. 2.The Columbia unit covers the early years of the United States from the founding of the country to the Civil War.
   哥伦比亚单元涵盖了美国早期从建国到内战的时期。
3. 3. The Columbia unit is designed to help students understand the complexities of American politics and society.
   哥伦比亚单元旨在帮助学生理解美国政治和社会的复杂性。