imagine及物动词 vt.在这些句子中的意思是：想像[W][+wh-][+(that)][+v-ing],如：
I can't imagine what has happened.
我想像不出发生了什么事.
You may imagine their astonishment at finding the room empty.
你可以想像他们发现房间里空无一人时那吃惊的样子.
我认为：1和3是对的.1中的how excited不能分,所以2不正确
3和4中how I hated that dog是宾语从句（连接词+主语+谓语）
不是感叹句,是主从复合句,所以不用感叹号