Study the following list of characteristics and identify the routing protocol.

Classified as an exterior gateway protocol used to route between autonomous systems.

A path$-$vector routing protocol, which analyzes the characteristics of all autonomous systems lying in the path between the router and each destination network so that it can form a nonlooping routing topology.

The routing protocol used by ISPs $($Internet Service Providers$)$ to make the Internet work.

a$.$ OSPF $($Open Shortest Path First$)$

b$.$ RIP $($Routing Information Protocol$)$

c$.$ BGP $($Border Gateway Protocol$)$

d$.$ IGP $($Internal Gateway Protocol$)$