わけだ
文法の解説は英語です。
用法
Used to express feelings like "No wonder -" or "It is natural that -" when the reason behind something is made clear
(普通/なAな/Nな) + わけだ
例文
このエアコン、20年前のだ。壊れるわけだ
This air conditioner is 20 from twenty years ago. No wonder it is broken