Chemical Engineering - Materials and Construction - Discussion

Austenitic stainless steels - the majority of stainless steels falling into this category are non-magnetic due to high levels of austenite. Despite the fact that some of the alloys, such as grades 304 and 316, contain iron, these materials are non-ferromagnetic. It is the crystal structure that is important for magnetic properties.

Why the answer is not D?

All stainless steel metals are a type of steel. That means their chemical composition contains iron. In most cases, stainless steel varieties with iron in their composition are magnetic. If the alloy has an austenitic crystal structure, then it's not magnetic.