難怪

難怪他今天這麼開心，原來他升職了。

No wonder he's so happy today, turns out he got promoted.

難怪你中文說得那麼好，你在台灣住了五年！

No wonder your Chinese is so good, you lived in Taiwan for five years!

難怪她沒來，她生病了。

No wonder she didn't come, she's sick.