If an iphone 4s ask for sim card to activate after restore is it a gsm (att) iphone?

My friend bought a iphone 4s the guy who sold it to him though it was a 4 anyways it was on the activation screen after doing a restore but it was asking for sim.one thing we both forgot to ask was if it was a sprint verizon iphone 4s or a at&t iphone 4s any help

Added (1). I don't want to unlock i just want a yes no awnser with details

Youtube how to jailbreak iphone 4s
How to unlock iphone4s

I believe you can use any kind of sims card but it still has to be an I phone sims card because I phones have smaller sims cards.

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