In Mandarin, we often use the passive voice for a few helpful reasons. The passive voice allows us to focus on what happened instead of who did it. Sometimes, we might not know who did it, or it might not matter. Here are some good reasons to use the passive voice:

1. Highlighting the Outcome:
   The passive voice can help us pay attention to what happened, not who did it. For example:

   • 这本书被读完了 (Zhè běn shū bèi dú wán le) - "This book has been read."
     Here, we focus on the book and that it’s finished.

2. Unknown Doer:
   When we don’t know who did something or it doesn’t really matter, the passive voice is great:

   • 窗户被打破了 (Chuānghù bèi dǎpò le) - "The window was broken."
     We don’t need to say who broke the window.

3. Formal Situations:
   In serious or written situations, the passive voice can sound more neutral:

   • 这个问题被讨论了 (Zhège wèntí bèi tǎolùn le) - "This issue has been discussed."
     This way, we don’t need to mention who is talking about it, which is good for formal writing.

4. Using the “把” Structure:
   The “把” structure usually shows someone doing something, but it can also show something happening to the subject:

   • 这本书把我读完了 (Zhè běn shū bǎ wǒ dú wán le) - "This book has completely captured me."
     Here, we see that the book has a strong effect on the speaker.

5. Focusing on Topics in Conversation:
   The passive voice helps us organize our conversations. It can be useful when discussing things:

   • 这件事被他说了 (Zhè jiàn shì bèi tā shuō le) - "This matter was mentioned by him."
     We start with "this matter" to grab attention.

6. With Conditions and Uncertainty:
   The passive voice is also helpful when we talk about uncertain situations:

   • 如果问题被解决 (Rúguǒ wèntí bèi jiějué) - "If the problem is resolved."
     This highlights fixing the problem rather than who fixes it.

These examples show us that the context and meaning matter a lot. The passive voice helps us focus on actions and results in Mandarin.