作状语：
Seen from the hill,the city is beautiful.
从山顶看,这座城市非常美丽。
Confined to bed (= Because she was confined to bed),she needed to be waited on in everything.
她卧病在床,什么事都需要人伺候。（作原因状语）
Having only book knowledge (= If you only have book knowledge),you will not be able to work well.
如果只有书本知识,你就不可能做好工作。（作条件状语）