A listed electrical box for use in fire-resistive assemblies is being installed in a 2 hour rated wall. Assuming there are no other electrical boxes on the opposite side of the wall, this installation long as the annular space between the electrical box and the wall membrane does not exceed?

b. 1/8"

Explanation:

In This scenario this installation does not require any penetration protection as long as the space between the electrical box and the wall membrane does not exceed 1/8 of an inch. This is mainly a safety precaution to prevent accident's such as an electrical fire or electrocution as well as meeting the specs for the rest of the house to be built perfectly without modifications.