I saw him seated at the back of the classroom.
I saw him seating himself at the back of the classroom. seat的用法比较特殊．当动词时有两种用法：
1．be seated. 例：They are seated there. 他们坐在那．
2．seat oneself. 例：They seat themselves there. 他们坐在那．
这也就可以解释前两句了，第一句是用法一，see sb. done. 省略be seated 中的be；第二句则是用法二， see sb. doing．
同样用法的词还有：hide（隐藏） 和 station(驻扎)
sit和seat都可以翻译成汉语中“坐下”的意思，但二者在英语中的用法却大相径庭。确切的说，sit多用于vi（不及物动词，即其后不带宾语）；seat则是vt（及物动词，其后一定要带宾语才能成立）而且seat的准确意思翻译为“使（某人）坐下”，这在汉语角度是不好理解的，所以我们在学习中必须要尊重英语的语法规则，从例句中掌握用法。for example,\请坐\表达为： Please sit down!或者please seat yourself!/please be seated!
第一句的用法是大家熟悉的，第二句可以看出seat用的时候必须用“人”来做宾语，即，seat oneself或被动形式sb. be seated两种形式。
“他坐在那”He sits there.& He seats himself there. & He was seated there. 这一点理解了，就要注意，seat一词的非谓语的形式也就只有seated.
eg. 1. When he entered the room, he found many villagers sitting/seated at the back of the room. 当他进入屋子的时候，发现很多村民坐在屋子后边。 2. Comfortably seated in a big arm chair, he read a novel.
他安逸地坐在椅子上读小说。
3. All the passengers, please remain seated before the plane lands safely.
所有乘客，在飞机安全着陆之前请坐在座位上不要动。
4. Can those _ at the back of the classroom hear me? A.seat B.sit C.seated D.sat
