stores where people visit

Question

Her brother, who is majoring in business administration, told her several interesting facts about marketing. The 'shower effect' is a marketing technique that places theaters, culture centers, restaurants, and other facilities that consumers frequently visit on the higher floors of a building. On the contrary, the 'fountain effect' places restaurants and grocery stores where people often visit on underground floors, guiding visitors to be exposed to attractive goods on the first floor. (from a textbook in my country)

The two bold parts have the same construction. I wonder which relatives are possible for the italicized. Especially, I doubt whether the usage of 'where' is grammatically correct.

1. theaters, culture centers, restaurants, and other facilities that consumers frequently visit
2. theaters, culture centers, restaurants, and other facilities which consumers frequently visit
3. theaters, culture centers, restaurants, and other facilities where consumers frequently visit
4. restaurants and grocery stores that people often visit
5. restaurants and grocery stores which people often visit
6. restaurants and grocery stores where people often visit

I guess 3 and 6 are ungrammatical. People visit stores. 'Stores' is an object of the verb 'visit'. So in the sentences in question, we should use relative pronouns 'which' and 'that', not a relative adverb 'where'. But an online grammar checker says 'where' is okay and 'which' is not. I don't get why. Please help me.

Answer 1

There is a rule for using 'which' and 'that', but it is often ignored in modern English, and many resources claim it no longer matters. 'Which' clauses are supposed to be parenthetical (ie useful or interesting, but you could omit them and your sentence would still make sense) and 'that' clauses are meant to be defining (essential information that identifies the subject). By that rule, you should use 'that', because specific stores are being targeted - ones that are visited frequently. But, all three of your choices - where, which, that - seem fine for this situation if you aren't too worried about obeying a rule unknown to many.

What would make them much better is if you reverse the last two words and say "stores that people visit frequently" rather than 'frequently visit' (or often, either seems fine). The reason is that you are speaking about 'consumers' which can mean consumers in general. Consumers 'frequently visiting' could mean that the store is regularly frequented but not necessarily by the same repeated customers. It would be like saying "hedgehogs often visit my garden". By saying that they 'visit frequently' makes it slightly clearer that the adverb is working on the verb 'visit' and that you are talking about the same ones returning.