Which of the following statements is incorrect about example data link protocols:

A.the Internet needs point-to-point links for dial-up modems, leased lines, and cable modems; therefore, standard protocols called Point-to-Point Protocols (PPP) is used to send packets over these links

B.SONET is commonly used over wide-area optical fiber links; to carry packets over these links some framing mechanism is needed; PPP runs on IP routers to provide this mechanism

C.ADSL (asymmetric digital subscriber loop) connects millions of home subscribers to the Internet; PPP is used to establish and configure the link and carry IP packets

D.PPP is a high level protocol, mostly used in the application layer