4
The sponsor's name and a physical address
The least interesting line, and the one to check first.
Every legitimate promotion names the entity running it and gives a real postal address. Not a web form. Not a support email. An address.
This exists so there is someone to serve papers on, somewhere to send a complaint, and somewhere the free entry route can point. It is also the single fastest legitimacy check available to you: a promotion that will not say who is behind it and where they are has told you something important in the space of one missing paragraph.
The same address requirement turns up again in email law, which is why every marketing message you receive has a postal address in the footer. Different statute, same instinct: somebody has to be findable.