复数： occurrences

The interspersing layers of ash show they were a regular occurrence .

夹杂着的灰层显示死亡是定期发生的。

If this is a first or second time occurrence , let it go .

如果这是第一次或者第二次发生，不要理会。

The mutation is a natural occurrence , as is the reaction to the drug .

这种突变是自然发生的，就像身体对于药物的反应一样。

Munsch says that each relationship is still unique , and infidelity remains a relatively uncommon occurrence .

munsch说每一种感情关系都是不同的，出轨仍然保持着一个相对不寻常的发生率。

Writing in science , they said fire occurrence rates had increased in 59 % of areas with reduced deforestation .

他们在《科学》杂志上撰文指出，在森林砍伐减少的地区，火灾发生率增加了59%。