if a problem arises later in the pregnancy.

如果在怀孕后期出现问题。

The birds also attack crops when the opportunity arises.

有机会的时候，鸟儿也会破坏作物。

This serenity arose in part from Rachel's religious beliefs.

这种平和状态在某种程度上源于雷切尔的宗教信仰。