My mind raced as I tried to work out what was happening.
我拼命地转动脑筋，想要搞清楚发生了什么事儿。
She couldn't believe it was all happening again.
她简直无法相信整件事又在重演。
I heard a commotion and went to see what was happening.
我听到一阵喧闹便去看看发生了什么事情。
There is very little likelihood of that happening.
几乎没有发生那种事情的`可能。
We hope to prevent anything unpleasant from happening.
我们希望防止任何不愉快的事发生。
I saw what was happening, but I was powerless to help.
我眼看着事情发生，却无力相助。