The upstream, downstream, and voice circuits channels supported by DSL modems and the channels created by multiplexors to support multiple simultaneous connections are examples of circuits. A) layered B) half-duplex C) logical D) parallel Which of the following is a TRUE statement about fiber optic cable? A) Unlike the types of multiplexing used for copper cables, wavelength division multiplexing (WDM) essentially increases the transmission capacity of a fiber optic cable by simultaneously supporting multiple connections that have the same transmission speed as the original un-multiplexed cable. B) Single mode fiber optic cable is able to support higher transmission speeds than multimode fiber optic cable because it has a larger core. C) Relative to metallic cable, fiber optic cable is a poor choice for harsh environments. D) All the above E) None of the above