1. What is the lowest layer of the OSI model at which LANS and WANS support the same protocols? A. Layer 2 B. Layer 3 C. Layer 4 D. Layer 5 2. What kind of device can monitor a connection at the demarc but cannot interpret data? A. CSU/DSU B. NID NIU C. D. Smart jack 3. What kind of network is the PSTN? 4. A. Packet-switched B. Circuit-switched C. Virtual circuit D. Dedicated line How many channels are in an ISDN PRI connection? A. 2B+D B. 2D+B C. 23D+B D. 23B+D 5. Which DSL standard has the fastest speeds immediately outside the CO? A. VDSL B. ADSL C. SDSL D. ADSL2+ tinal ice to conarate data on a channel?