请帮我解释一下几个词组．

call at:

vt. 访问(停靠)

例句与用法:
1. The ship called at several ports between Dalian and Shanghai.
这艘船在大连和上海之间停靠了几个港口。

2. I shall call at his home tomorrow.
我明天要到他家里拜访。

3. I wanted to call at him the minute he arrived.
我刚要打电话给他, 他就来了。

4. I'd love to, but my father's go to call at me.
我倒是希望来的，可是我的父亲要来看我。

5. The postman always calls at 7.30.
邮递员一贯7时30分来.

英英解释:
动词call at:

1. enter a harbor
同义词：out in

call on:

vt. 号召(约请,访问)

例句与用法:
1. Our salesmen call on their best account twice a month.
我们的销售人员每月访问最好的客户两次。

2. The government calls on the youth to donate their blood voluntarily.
政府号召青年义务献血。

3. Tomorrow I'll pay a call on him.
明天我将要去拜访他。

4. I'd like to call on you this Sunday.
我想这个星期天来找你。

5. If I were free now, I might call on him.
如果我有时间，我可能会去看他。

6. I'm going to call on one of my former classmates.
我要去看望我的一位老同学。

7. All you have to do is call on the house phone.
我只要做的就是拨个室内电话。

8. OK if I call on you tomorrow?
我明天来找你行吗?

英英解释:
动词call on:

1. have recourse to or make an appeal or request for help or information to
同义词：turn

call in:

召集,召来

例句与用法:
1. He is ill; you should call in the doctor right away.
他病了, 你应该立即请大夫来。

2. We could call in on Patrick on the way to your mother's.
我们到你母亲家去, 不妨顺路到帕特里克家串个门儿.

3. I'll take the (telephone) call in my office.
我想在我的办公室里接这个电话.

4. Will you call in at the supermarket for some eggs and milk?
你顺便去超级市场买些鸡蛋和牛奶好吗?

英英解释:
名词call in:

1. a telephone call to a radio station or a television station in which the caller participates in the on-going program
同义词：call-in

动词call in:

1. summon to enter

2. summon to a particular activity or employment

3. pay a brief visit
同义词：visit, call

4. take a player out of a game in order to exchange for another player

5. make a phone call

6. demand payment of (a loan)
同义词：call

7. cause to be returned
同义词：recall, call back, withdraw

call at打给某人 拜访 停靠
call on号召 呼吁 邀请 访问，要学生回答问题
call in召集 召来 来访

1。访问，打给某人
2。号召，邀请
3。召集，来访