when metals react they Aremove electrons from the other reactant Bcause an increase in the oxidation number of another reactant Ccan form both ionic and covalent bond with other reactants Dbehave as reducing agents

The correct answer is D. behave as reducing agents.

Explanation:

A. Remove electrons from the other reactant: This is not true. Metals do not remove electrons from other reactants. Instead, they lose or donate their own electrons to other reactants.

B. Cause an increase in the oxidation number of another reactant: This is true, but it is not the best answer. When a metal loses electrons (is oxidized), it causes the oxidation number of the other reactant to increase. However, this is a result of the metal acting as a reducing agent, which is a more comprehensive answer.

C. Can form both ionic and covalent bond with other reactants: This is not always true. Metals typically form ionic bonds, not covalent bonds. Covalent bonds are more common between nonmetals.

D. Behave as reducing agents: This is the best answer. In a redox (reduction-oxidation) reaction, the substance that loses electrons (in this case, the metal) is called the reducing agent. So, metals behave as reducing agents because they lose electrons and cause the other reactant to be reduced (gain electrons).