“be＋過去分詞”這個結構並不都是被動語態，也可能是系表結構。被動語態與系表結構主要區別是：被動結構表示一個動作，而系表結構表示主語的特點或所處的`狀態，試比較下面的句子：
被動結構
The enemy was soon surrounded by us.
系表結構
The house is surrounded by trees.
被動結構
She was bitten by the dog in the darkness.
系表結構
I was excited by the news that my husband got promoted.
