Narwhals frequently dive to deep waters - the deepest recorded in this study was 1773 metres.

独角鲸经常潜入深水，在这项研究中，最深记录的是1773米。

Although it was Sondheim's only Top 40 hit, his songs are frequently performed and recorded by cabaret artists and theatre singers in their solo careers.

尽管这首歌是桑德海姆唯一一首进入前40名榜单的单曲，但是很多酒店以及戏剧歌手在单独表演或者录制唱片时都常常选用他的歌曲。

It was the first and frequently visited country from Southeast Asia recorded in the historical records of ancient China.

是历史上第一个出现在中国古代的史籍上的东南亚国家，也是中国古代史籍中经常出现的东南亚国家。

These institutions may not be recorded in any formal records and are frequently unknown except to local participants.

这些制度可能没有以任何正式记录的方式记载下来，并且通常对于非本地参与者而言是不为人所知的。