What is an oxidation reaction? A. A reaction in which an atom gains 1 or more protons

B. A reaction in which an atom loses 1 or more protons

C. A reaction in which an atom loses 1 or more electrons

D. A reaction in which an atom gains 1 or more electrons

(Answer is C)

in an oxidation reaction an element loses one or more electrons

Explanation:

An oxidation reaction was originally defined as combining an element with oxygen, e.g. 2Ca + O2 —> 2CaO

Now we consider an oxidising agent as an electron acceptor, so the reaction need not include oxygen, e.g. Ca + S —> CaS. Ca loses electrons to S.