Inserts for cellular metal floor raceways shall be leveled to the floor grade and sealed against the entrance of _____.
d) all of the above
See answer and applicable Code reference
The correct answer is: a) concrete
Article 374 covers the use and installation requirements for metal floor raceways. As noted in Sec. 374.10, "Inserts shall be leveled to the floor grade and sealed against the entrance of concrete. Inserts shall be of metal and shall be electrically continuous with the raceway."