1. This is the classroom in which I met her.
2. This is the playground at/on/in which I met her.
3. This is the coffee shop at/in which I met her.
4. This is the street in/on which I met her.
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Can we use all the prepositions before 'which'? Which ones are incorrect?
Yes, all of those prepositions are OK in these sentences. I'd probably omit "in" in sentence 2, but that's a preference, not necessarily incorrect.
In these sentences, the prepositions "in," "on," and "at" can be used before "which" to show the location where the speaker met someone.
Here's an explanation of the correct usages:
1. "This is the classroom in which I met her."
- This sentence suggests that the speaker met her in a specific classroom.
2. "This is the playground on which I met her."
- This sentence implies that the speaker met her on a specific playground.
3. "This is the coffee shop at which I met her."
- This sentence indicates that the speaker met her at a particular coffee shop.
4. "This is the street on which I met her."
- This sentence suggests that the speaker met her on a specific street.
To determine which prepositions to use, consider the specific location where the meeting took place. "In" is used for enclosed spaces like classrooms, "on" is used for surfaces like playgrounds and streets, and "at" is used for specific places like coffee shops. So, all of the prepositions used in these examples are correct.