31. 

The _____ layer is the layer closest to the transmission medium.

A. transport
B. network
C. data link
D. physical
E. None of the above

32. 

What is the name of the device that connects two computers by means of a telephone line?

A. Tape
B. modem
C. bus
D. cable
E. None of the above

33. 

What is the main difference between DDCMP and SDLG?

A. DDCMP does not need special hardware to final the beginning of a message.
B. DDCMP has a message header
C. SDLC has a IP address
D. SDLC does not use CRC
E. None of the above

34. 

On a class B network, how many subnets are available with a subnet mask of 248?

A. 2
B. 6
C. 30
D. 62
E. 126

35. 

Ethernet networks can be cabled in a number of topologies, depending on what works best in each environment. As more nodes are added, the efficiency of Ethernet decreases. Select the best answer as to why Ethernet becomes less efficient as size increases.

A. Network collisions occur
B. Repeaters cannot increase the signal strength sufficiently
C. Cable terminators do not reflect the signal properly
D. Cable terminators do not absorb the signal properly
E. "Line echo" occurs due to the impedance of the cable