In a reaction, a reducing agent A. gains electrons. B. causes the oxidation of another compound. C. is reduced in a reaction. D. is a spectator ion. E. lowers the oxidation number of an atom in another compound.

The correct answer is option E.

Explanation:

Reducing agents are defined as the agents which reduces the other substance and itself gets oxidized. These agents undergoes reduction reactions

Reduction reaction is defined as the reaction in which an atom gains electrons. Here, the oxidation state of the atom decreases or lowers.

Oxidizing agents are defined as the agents which oxidize other substance and itself gets reduced. These agents undergoes reduction reactions.

Oxidation reaction is defined as the reaction in which an atom looses its electrons. Here, oxidation state of the atom increases or highers.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8