What do routers do in a network?

Question $14$ options:

a$)$

Routers connect different parts of a LAN together but cannot connect to the WAN

b$)$

Routers move data between separate LAN's, often by linking them to WAN lines

c$)$

Routers are Layer $2$ devices, so they can connect to WAN's but not LAN's

d$)$

Routers are Layer $2$ devices, so they can connect to LAN's but not WAN's