主语补语就是带有复合宾语（即宾语+宾语补语）的句子变成被动句以后,主语的动作（由动词不定式充当）、性质（由形容词词等充当）、属性（由名词充当）.
例如：The thief was seen to enter the house last night.昨晚有人看见小偷进入那所房子.
to enter the house 为主补.
(1)We are Chinese.为表语非主补.
(2)Baby seems hungry.(同上)
评论：不少人对形容词用法分不清,现举例说明：
asleep通常做表语：The children are both asleep.两个孩子都睡了.
但是如果它的主语变成了句子的宾语时,它就做宾语补语了:People who find hibernating animals asleep often think that they are dead.人们看到处于冬眠状态下的动物,常常以为它们是死的.
