1．call on  拜访某人，号召

We will call on Mr. Li tomorrow．

We are called on to help those in trouble．

2．call at  拜访某地

I called at your office yesterday, but you were not in.

3．call for  需要；要求；邀约（人）；取（物）

Success called for hard work．

call for a doctor  去请医生

4．call in   请来;收回

Mother is badly ill, so call in a doctor at once．

5．call up  打电话；征召；回想起

I called Tom up and told him the news．

In most countries men are called up at the age of 18．

As I grew up in a small town at the foot of a mountain, the visit to the village called up scenes of my childhood．