a question about arrivewhat is the different between arrive in and arrive at?thanks for help.

arrive
[əˈraiv]
vi.
到达, 来
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arrive at
1.到达, 来到
One day a letter from my father arrived at the school.
有一天, 学校收到了我父亲的一封信。

2. 达成, 获得, 作出(决定)
I have arrived at the conclusion that he is a very intelligent boy.
我已得出结论, 他是一个非常聪明的孩子

arrive at + small place
for example: She arrived at the bus station yesterday night.
arrive in + bit place
for example: They will arrive in Beijing tomorrow.

arrive in 跟大地点
arrived in this country
arrive at 跟小地点
arrived at the airport

in是大地点,at小地点.arrive in shanghai ,arrive at airport.

arrive in 通常接 比较大型重要的地点 如 到达某个国家或城市；
arrive at 通常接小型的比较具体的一些场所,如学校、医院、车站等.