When required to work in an area where explosive gases may accumulate, you should use hand tools which are __________.

Correct Answer: Option D — non-ferrous

In hazardous environments where explosive gases may be present, non-ferrous tools are required to prevent the generation of mechanical sparks. Ferrous metals, such as steel, can produce sparks upon impact with other metals, which could serve as an ignition source for flammable vapors in the vicinity.