何故

tā hé gù zhì jīn wèi dào

她何故至今未到？

Why hasn't she come yet?

háng bān hé gù bèi qǔ xiāo

航班何故被取消？

Why has the flight been cancelled?

bù zhī hé gù tā shì tú shǔ mián yáng

不知何故，他试图数绵羊。

He was trying, for some unknown reason, to count the sheep.

nǐ hé gù bèi tuì xué

你何故被退学？

Why were you dropped out?

tā hé gù huǐ hūn

她何故悔婚？

Why did she repent of her marriage?