“be＋过去分词”这个结构并不都是被动语态，也可能是系表结构。被动语态与系表结构主要区别是：被动结构表示一个动作，而系表结构表示主语的特点或所处的状态，试比较下面的句子：

　　被动结构

　　The enemy was soon surrounded by us.

　　系表结构

　　The house is surrounded by trees.

　　被动结构

　　She was bitten by the dog in the darkness.

　　系表结构

　　I was excited by the news that my husband got promoted.