唔識用which, in which 等情況

Where 是跟地方有關時候用的代名詞或提問題：
Where were you born?
Where do you live?

但where所指的很廣，當他人回答了你問題之後，你仍可能有再深入的問題。那時候，你便要用到which (in which, on which, at which)再加上你所提問的要點。
Where were you born? I was born in China.
In which city were you born? I was born in Guangzhou.
In which hospital were you born? I was born in hopsital #3.

在做relative clause的時候，如果副句內的主語之前是沒有介詞，那麼通常relative clause pronoun都會用where；不然的話，就可以用preposition+which或是where.

John was born in America.
America was the country in which John was born.
America was the country where John was born.

John stays at the Hilton.
Hilton is the hotel at which John stays.
Hilton is the hotel where John stays.

但若是preposition+which並沒有指示地方，那時候你就不可以用where改寫句子。例如：
There are five parks in the city, in which two have a jogging trail.
(There are five parks in the city. Two of these five parks have a jogging trail.)

In which occasion did John say that he wanted to leave his job?

Who 的用法是當relative clause的主語是人稱時。例如：
John likes to read. John is my friend.
John, who likes to ready, is my friend. (non-defining)

I know two friends who are called John. (defining - not just any friends, the friends who are called John)
The John who likes to read has long hair. (defining - not both John, but the one who likes to read)

We seldom see the form "in which" as that is just a rearrangement in the structure.

Consider the following:
1. I lived in this house when I was small.
2. This is the house in which I lived when I was small.
3. This is the house which I lived in when I was small.
4. This is the house where I lived when I was small.
5. A: Give me the orange ball.
B: There are so many balls, and some are in the same colour, I can't distinguish which is which and which is whose.
A: Give me the one which has a blue dot on it.

2, 3 and 4: The main and the only one difference is that the word "in" is rearranged into different location. in which in this case could be replaced by where.

5. Refer to to line given by B. "which" could be considered as a pronoun in this case, refering "whcih ball" and the 2nd "which" is refering to "A's orange ball". the 3rd "which" is refering as "which orange ball"


"which" is used following something.
"who" is used following someone.