偶然发生

例句：

1. 1. He was in a terrible accident and had to be hospitalized for several days.
   他遭遇了严重的事故，不得不住院治疗几天。
2. 2. The car accident killed all the passengers on board.
   那场车祸导致船上的所有乘客死亡。
3. 3. Accidents can happen at any time, so it's important to always be cautious.
   事故随时可能发生，因此总是保持谨慎很重要。