How are MC, AC (BX) and NM (Romex) cables required to be secured?

     MC (Metal Clad Cables) contains equipment grounding conductors.  The smallest size available according to the NEC that shall be used is # 18 awg copper.  Note that some fire rated conductor material is of nickel or nickel-coated copper.  There is also cable used for Optical Fiber called MC-OF.  The size of the equipment grounding conductor is sized based on Table 250.122 of the National Electrical Code however when part of a cable assembly such as MC, AC, BX, or Romex, NM cable the size required is already determined for you.  The allowable