Yep. None of the above.

The choice of grounded conductor was not present. But that is the right answer. So by selecting d. you did good.

Use this Google search box to find topics on this website: 

The next Master Electrician Course in Port St. Lucie begins January 9th, 2010. Details HERE.

Products For Sale
  dularson@bellsouth.net  
  1998-2010 by David Ullian Larson
Advertise at ElectricianEducation.com    
Link Exchange Solicited For Appropriate Products 
Companion websites include:
http://www.electricianmath.com  
http://www.technicianeducation.com
http://www.2011nec.com (not yet)

Other websites which may be of interest:
http://www.6901st.org 
http://www.oldpostcardsforsale.com 
http://www.swedenroots.com
http://www.visiteuropeonline.com
http://www.houseflipguide.com
http://www.greenfieldvillageonline.com