例句：
That doesn't happen very often.
那不常发生。
This must never happen again.
这种事再也不能发生了。
How on earth did that happen?
那到底是怎么发生的？
例句：
That doesn't happen very often.
那不常发生。
This must never happen again.
这种事再也不能发生了。
How on earth did that happen?
那到底是怎么发生的？