ask about/ask after/ask for/ask of

ask about 是指“询问某人或某事”：

1. He asked him about his business. 他询问他的生意如何。

2. The man went to the school to ask about his boy. 那个人到学校去了解他孩子的情况。ask after 是指“问候某人”：

3. I asked after my sick friend. 我问候了生病的朋友。

4. They all seemed very concerned, and your health was asked after. 他们大家似乎都十分关切，并问候了你的健康情况。

ask for 是指“请求某物、要某物”：

1. He asked for information. 他要求得到信息。

2. He came to ask for a loan. 他来借款。

3. I want to ask for a two-day leave of absence. 我想请两天假。

ask of 是指“向某人要求某事”：

1. May I ask a favour of you? 可不可以请您帮个忙？

2. I asked of him the favour of a loan. 我求他帮助贷款。