如果你需要帮助，请按铃。

Please press the ___bell if you need help.

就在我准备离开的时候，铃响了。

The ___bell rang just as I was about to leave.

你听到门铃了吗？没有，但我听到了电梯的铃声。

Did you hear the doorbell? No, but I heard the ___bell for the elevator.