Foam Concentration Testing

Here are three statements about use of extension cords. According to the fire code, only one is true. Which one? (click a letter):

A. It is NEVER okay to use an extension cord.

B. If used properly, an extension cord may be used on a temporary basis.

C. If it is of the proper gauge and tacked down or under a rug, you can use an extension cord on a permanent basis.