Network control protocols are used in PPP to establish and terminate data links, provide authentication capabilities, manage network congestion, and allow multiple Layer 3 protocols to operate over the same physical link (option 4).
The DS0 standard has a data transmission rate of 64 kb/s (option 2).
Key differences between LANs and WANs are found in Layer 1 (Physical Layer) and Layer 2 (Data Link Layer) of the OSI model (options 1 and 2).
The Cisco implementation of the HDLC protocol is the default encapsulation for serial interfaces on Cisco routers (option 3).