require/request/demand

demand 是指“强烈要求”，而不是指“请求”，因而含有“要求对方服从”的意思，口气强硬：

1. The workers are demanding more money. 工人要求增加工资。

2. I demand to see my lawyer. 我要求见我的律师。

require 也是指“要求”，而不是指“请求”，但它强调“客观上的需要或必须”：

1. You are required by law to send your children to school. 法律规定你必须送孩子上学。

2. The situation requires that I should be there. 情况需要我在那里。

request 则是指“请求”，用于客气、有礼貌的场合：

1. I request him to help. 我请求他帮忙。

2. Passengers are requested not to smoke (= a notice in a bus). 请勿吸烟(公共汽车中的告示)。

请改正句中的错误：

1. I bought all I requested at the grocer's.

2. They formally required him to visit China.