⋯⋯，否则⋯⋯
Explanation
用于表达必须采取某种行动，否则会产生负面后果的假设复句结构。
Used to express a conditional relationship where failure to take a required action will lead to negative consequences.
Examples
我要认真复习，否则考试会不及格的。
I need to review seriously, otherwise I’ll fail the exam.
记得带卡，否则进不了办公室。
Remember to bring your card, otherwise you won’t be able to enter the office.
上课前一定要预习好生词和课文，否则就听不懂老师讲的。
You must preview the new words and text before class, otherwise you won’t understand what the teacher says.
Related Grammar Points
假如⋯⋯，（就）⋯⋯HSK 4四51
句子的类型 · 假设复句
该结构用于表达假设条件及其可能结果，'假如'引导假设条件分句，主句常用'就'连接结果（可省略）。
This structure expresses hypothetical conditions and their potential outcomes. '假如' introduces the condition clause, while the main clause typically uses '就' to connect the result (which can be omitted).
Examples (2)
假如有困难，你一定要告诉我。
If you encounter difficulties, you must tell me.
假如能通过这个考试，我就可以拿到学校的奖学金了。
If I can pass this exam, I would be able to receive the school's scholarship.
万一⋯⋯，（就）⋯⋯HSK 4四52
句子的类型 · 假设复句
该结构用于假设某种可能发生但不太理想的情况，并提前说明应对措施。'万一'引出假设条件，'就'连接对应的结果或建议。
This structure is used to propose contingency plans for unlikely but possible situations. '万一' introduces the hypothetical condition, while '就' connects the corresponding response or suggestion.
Examples (2)
万一我没来，你就自己先去吧。
In case I don't show up, you should go ahead by yourself.
一定要把你们的护照带上，万一需要，没带就麻烦了。
Make sure to bring your passports. In case they're needed, not having them would cause trouble.