有英语问题不懂!help me!

题目

有英语问题不懂!help me!
1> The boy seating himself was my brother.
2> The boy seated was my brother.
3> He was surprised to see some villagers seated there.
4> To his surprise,hesaw some villagers seating themselves at the back of the classroom.
不明白1>和2〉为什么一个用ed,一个用ing?明明都是the boy主动坐的,2〉应该也是ing呀,难不成是被动?不可能.3〉和4〉也是不明白为什么一个ed,一个ing?

答案

说到底,seat是及物动词,作动词使用后面一定要加宾语.
2中seated是修饰the boy,过去分词做定语.The boy（seated）was my brother.后面的句子同样的理由.