A is to B what C is to D. what 是连接副词
2. When she returned home, she found the window open and something stolen.句中open是形容词作宾补 可以表示状态
如果用opend则意思不一样 因为过去分词具有动词特征
3.The car needed ____.(repair)可以填写 repairing.或to be repaired