All questions and answers are based on the 2011 NEC.
Q. What types of equipment grounding conductors does the NEC allow?
A. An equipment grounding conductor can be any one or a combination of the following [250.118]:
1) A bare or insulated copper or aluminum conductor sized in accordance with 250.122.
2) Rigid metal conduit (RMC).
3) Intermediate metal conduit (IMC).
4) Electrical metallic tubing