sad的副词是

sad的副词sadly；

sadly

adv. 悲哀地；悲痛地

例句

The child stands there sadly.

那孩子伤心地站在那里。

Sadly, that feeling never came.

可悲的是，我从未有过这种感觉。

Sadly, this has not happened.

遗憾的是，这些都没有出现。

Sadly, there is nothing there.

可惜的是，一无所获。

He answered my question sadly.

他悲伤地回答我。

But, sadly, sometimes it happens.

然而，不幸的是，它有时偏偏也会发生。