Oxidation State

The oxidation state, often called the oxidation number, is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were $100$ % ionic. Oxidation states are typically represented by integers, which can be positive, negative, or zero. What are the respective oxidation states (oxidation numbers) of the underlined atoms below?

$A: \underline{\text{C}}\text{H}_4 \quad B: \text{K}\underline{\text{Mn}}\text{O}_4 \quad C: \underline{\text{Fe}}_2\text{O}_3$