call on／upon

1．visit sb．formally either socially or on business 拜访某人

We'll call on you very shortly．我们不久就会去拜访你。

The deputies called upon the mayor to invite his cooperation in their work．代表们拜访了市长，请他在工作上给予合作。

2．ask；invite；make a demand on；appeal to sb．to do sth．要求；请求；号召

The government called on the people to practise economy．政府号召人们厉行节约。

We have to call upon the parents to help us educate the teenagers．我们必须呼吁家长协助我们教育青少年。

The Chairman called on Mr．Brown to speak at the meeting．主席请求布朗先生在会上发言。