In the park, some old people were seen seated on the benches, chatting happily.

参考译文：在公园里，一些老人被看见坐在长凳子上，愉快地聊天。

A. having seated  B. to seat   C.seating  D. seated

see sb seated on the benches 结构

句子语法结构分析如下

地点状语：In the park( 在公园里）

主语：some old people（一些老人们）

谓语：were seen（被看见）

主语补足语：seated on the benches（坐在长凳上）

（过去分词短语作主语补足语）

伴随状语：chatting happily（愉快聊天）

(1)主动语态：see sb seated on the benches

（看见某人坐在长凳上）(过去分词短语作宾语补足语）

(2)被动语态：sb be seen seated on the benches

（某人被看见坐在长凳上）（过去分词短语作主语补足语）

答案为 D。B 不行，为什么？请顺便解释一下seat 的用法，以及与 sit 的区别，说 seat 是及物动词，它就得用 seated 的形式，太迷茫了。谢谢!

解答如下：

seat  vt使坐下;使就座

(英文解释：If you seat yourself somewhere, you sit down）

He waved towards a chair, and seated himself at the desk. 

他挥手指了指一把椅子，自己在书桌旁坐了下来。

(1) A seat B   A使B坐下

(2)A be seated A使自己坐下=A sit down=A take a seat

(3)one seat oneself 某人使某人自己坐下=one sit down=one take a seat

(4)one be seated 某人使自己坐下=one sit down=one take a seat

Please seat yourself, sir.

请坐,先生。

He seated himself at the desk.

他自己坐在桌子旁。

He seated us and called to his daughter to bring tea.

他让我们坐下,然后叫他女儿端茶来。

I seated him in the chair.

我让他在椅子上坐下来。

The mother seated her child on a bench.

母亲把孩子放在凳子上坐好。

We seated our guest to the right of the chairman.

我们请来宾坐在主席的右边。

(2)seat  vt(房间、车辆)可坐…人，容纳…人

(英文解释：A building or vehicle that seats a particular number of people has enough seats for that number）

主语+seat+基数词+名词=主语可以给多少人/事物提供座位/容纳多少人/事物

Theatre seats 570 people. 

那个剧院可容纳 570 人。

We can't seat all these people.

我们无法为所有这些人提供座位。

She is seating an old pair of trousers.

她正在修补旧裤子的后裆。

Our table seats eight.

我们的桌子可坐8人。

Our auditorium can seat 1500 people.

我们的礼堂能容纳1500人。

Seat 和 Sit区别如下

seat和sit作为动词，都可以表示“坐”的意思。

(1) seat是及物动词，比较正式，常以被动形式表示主动意义。

He is seated between Jack and Tom.　

她坐在杰克和汤姆之间。

Please be seated. (=Please seat yourself.) 请坐。

(2) sit通常作不及物动词用，比较口语化。

The students are sitting at their desks.　

学生们正坐在课桌旁。

Sit down, please. 请坐。

Let's sit down and then you can say what's up. 

咱们先坐下来，然后你把事情告诉我。

 Now sit down and make yourself comfortable. You must be very tired. 

现在坐下来，让自己舒服些，你一定很累了。

(3) seat还可作名词用(而sit只能作动词用)，常见短语take a seat (相当于have a seat或take one's seat) ，意为“坐下，就座”。

Take your seat, please. 请就坐。

."Take a seat," he said in a bored tone. 

“请坐，”他不耐烦地说道。

 Won't you take a seat? 

请坐好,好 吗 ?

'Pray take a seat, sir.' 

“ 请坐, 先生. ”

. 'Jim,'said Dr Livesey,'take a seat.' 

“ 吉姆, ”利维塞大夫说, “ 你坐吧. ”

 Please take a seat -- the manager will soon be here. 

请坐, 我们经理一会儿就来.

 Come in please, and take a seat.  

请进.请坐.

 You can take a seat now. 

现在你找个座位坐下吧.

 Come in and take a seat. 

请进来坐.

为什么“使自己坐下”是A be seated A，而不是A  seated呢？为什么要被动呢？see sb seated on the benches 结构中 seated 是什么词？过去分词还是形容词？如果是过去分词，那不是被坐在....了么？为什么seat 常以被动形式表示主动意义被动形式怎么理解成主动意义？谢谢

seat  vt. 使某人坐下

A 使B坐下= A seat B

某人使某人自己坐下=one seat oneself

别人是自己坐下=one be seated