The child is quite black, only it has white PAWS, but with that exception, it has not a single white hair on its whole body; this only happens once every few years, you will let me go, won't you?

这个孩子除了爪子是白色的，浑身黑黝黝的，连一根白毛都没有。这是好几年才会碰上的事情，你当然会同意我去的，是吗？

youdao

The child is quite black, only it has white PAWS, but with that exception, it has not a single white hair on its whole body, this only happens once every few years, you will let me go, won't you.

这个孩子除了爪子是白色的，浑身黑黝黝的，连一根白毛都没有。这是好几年才会碰上的事情，你当然会同意我去的，是吗？

youdao

This event happens only once: before the data set is filled with data.

该事件只会发生一次：在数据集合被数据填充之前。

youdao

India's Kumbh Mela festival, the largest gathering in the world, happens only once every 12 years and kicked off this week in Allahabad.

BBC: In brief: India��s Kumbh Mela festival begins