A covalent bond is formed between two non metal elements. Now out of elements A, B and C, the element B and element C are non metals. Thus the elements B and C will form covalent bonds. An electrovalent bond is formed between a metal and a non metal. Now, out of the above elements, the element A is metal and element C is a non metal. Thus elements A and C will form an electrovalent bond. Even though the element B is also a non metal, but it usually does not form electrovalent bonds.
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