This question tests the fundamentals of routing at the network layer (Layer 3) of the OSI model. Routing is the process by which a network decides the path a packet should take from source to destination across interconnected networks, and the device that performs it is the router.

Evaluating each statement:

• S1 — TRUE: Routers operate at the network layer. They read logical (IP) addresses to make forwarding decisions between different networks, which is precisely a Layer 3 function. (Switches, by contrast, work mainly at Layer 2 using MAC addresses.)
• S2 — TRUE: Routing is exactly the determination of the forwarding path a packet follows, so this is a correct description of its purpose.
• S3 — FALSE: Static routes are entered and maintained manually by the network administrator; they do not update on their own when the topology changes. Automatic updating is the hallmark of dynamic routing, so attributing self-updating to static routing is incorrect.
• S4 — TRUE: Dynamic routing protocols such as RIP, OSPF and BGP exchange reachability and cost information between routers so that each can build and continually refresh its routing table.

Since S1, S2 and S4 are true while S3 is false, the correct combination is only S1, S2 and S4. The pairings that include S3 or omit either S1 or S4 leave out a valid statement or include the false one, so they are wrong.