suddenly failure

例句：

1. 1.He suddenly appeared at the door.
   他突然出现在门口。
2. 2. She suddenly realized that she had forgotten her keys.
   她突然意识到她忘记带钥匙了。
3. 3.The sudden rain made the streets wet and slippery.
   突如其来的雨让街道变得湿滑。