Answer:
4-They are setup manually
Explanation:
BGP neighbor relationships formed "They are set up manually."
This is evident in the fact that BGP creates a nearby adjacency with other BGP routers, this BGP neighbor is then configured manually using TCP port 179 for the actual connection, which is then followed up through the exchange of any routing information.
For BGP neighbors relationship to form it passes through different stages, which are:
1. Idle
2. Connect
3. Active
4. OpenSent
5. OpenConfirm
6. Established
