The correct answer is b. Iron II sulfate.
FeSO4 is composed of iron (Fe), sulfur (S), and oxygen (O). In this compound, iron has a +2 oxidation state, which is why it is referred to as Iron II sulfate. The Roman numeral II indicates the oxidation state of iron in this case. This is important because iron can exist in multiple oxidation states, such as +2 and +3, and distinguishing between these states is essential for accurately naming the compounds.