Which of the following is a possible oxidation state?

The correct answer is +5. This choice represents a common oxidation state for various elements in group 15, such as phosphorus and arsenic, where they can share or lose electrons leading to a positive charge.

The concept of oxidation state is based on electron transfer and the ability of an element to lose or gain electrons in the formation of compounds. Elements can have multiple oxidation states, but certain states are more commonly encountered than others. For example, +5 is a recognized and stable oxidation state for several central atoms in coordination chemistry and metabolic processes.

In contrast, -4 and -5 are less commonly accepted as oxidation states. While elements like carbon can exhibit a -4 oxidation state (especially in compounds like methane), -5 is rare and not generally encountered in stable compounds. Furthermore, +6 represents a stable oxidation state for elements such as sulfur in sulfate compounds, while higher oxidation states are often seen in transition metals and heavier elements. Thus, among the given options, +5 is a possible and valid oxidation state.