Relative pronouns

[Carvalho]

I was doing some exercises on relative clauses, and now I have doubts about which pronoun I can use.
For example if I'm joining these two sentences:

A very ancient cathedral was destroyed in the earthquake. It is now being rebuilt.
Can I say:
A very ancient cathedral which/ that was destroyed in the earthquake is now being rebuilt. Can I use both pronouns? Or not? Why?

And in these two sentences:
People have complained about the noise. They live in flats.
Can I say:
People that / who live in flats have complained about the noise.
I can't understand the difference, thanks! :oops:

[Mister Micawber]

For restrictive clauses you can use either 'which or 'that', but 'that' is more common. For humans, you can use 'that' or 'who', but 'who' is more widely accepted.
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Native English teacher at Mister Micawber's