"We recommended hemorrhage drills just like fire drills. For an event that doesn't happen very often, people need to practice.

VOA: standard.2010.06.23

I know this doesn't happen very often. But let's just say this happened.

我明白这种情况并不常见，但我们假设它确实发生了。

I'd better 课堂 - SpeakingMax英语口语达人

So it's OK to not specify. I want to point out, pz whether you're in the p x, the p y, or the p z, unless a question specifically m asks you to specify the m sub l, which occasionally will happen, but if it doesn't happen you just write it like this.

我想指出的是，无论你在px，py或，除非一个问题特别地,让你指出l下面的，这种情况有时会发生，这样就可以了,但是如果它不做要求你们写成。

麻省理工公开课 - 化学原理课程节选

Like the European Union, the US system doesn't just happen to be slow in finding solutions.

BBC: A system designed to be this way

"A conference like this doesn't just happen, " David Jones told his audience.

BBC: Sergeant Wilson, Corporal Jones and the prime minister

"The first thing to remember is that drowning doesn't just happen, " says Alison Osinski, water safety expert and president of Aquatic Consulting Services.

CNN: Water safety expert: 'Drowning doesn't just happen'