The correct answer is option 3: Fluorine. Fluorine is an element that never exhibits a positive oxidation state in any of its compounds.

To understand this, let`s first define oxidation state. Oxidation state is the hypothetical charge that an atom would have if all the bonds in a compound were completely ionic. It is a measure of the degree of oxidation of an atom in a compound.

Oxygen (option 1) is capable of exhibiting positive oxidation states, such as in peroxides (e.g. H2O2), but it can also exhibit negative oxidation states in compounds like water (H2O).

Chlorine (option 2) can exhibit both positive and negative oxidation states. For example, in compounds like sodium chloride (NaCl), chlorine has a negative oxidation state of -1, but in compounds like chlorine gas (Cl2O), it can have a positive oxidation state of +1.

Carbon (option 4) can also exhibit positive oxidation states, such as in carbon dioxide (CO2) where it has an oxidation state of +4.

Therefore, the correct answer is option 3: Fluorine, as it only exhibits negative oxidation states in its compounds and never exhibits a positive