“万一出事怎么办？”用英语怎说？

如果...将会怎么样 应用what if,
例句与用法:
1. What if it is true?
如果这是真的又该如何呢？

2. What if he doesn't agree?
如果他不同意该怎么办呢？

3. What if he comes back now?
如果他现在回来怎么办？

我认为可以翻译为：What if there is an accident?

How do the event of accident?

How if has an accident to manage?