Which of the following explanations best describes the process by which the elements calcium and oxygen combine to form the binary compound calcium oxide? 2Ca(s) + O2(g) → 2CaO(s)

A. Calcium has a low electronegativity, so it loses electrons, resulting in a positively charged ion. Oxygen has a high electronegativity, so it gains electrons, resulting in a negatively charged oxide ion. The oppositely charged ions are attracted to each other, forming calcium oxide.
B. Calcium has a low electronegativity, so it gains electrons, resulting in a negatively charged ion. Oxygen has a high electronegativity, so it loses electrons, resulting in a positively charged oxide ion. The oppositely charged ions are attracted to each other, forming calcium oxide.
C. Calcium has a high electronegativity, so it loses electrons, resulting in a positively charged ion. Oxygen has a low electronegativity, so it gains electrons, resulting in a negatively charged oxide ion. The oppositely charged ions are attracted to each other, forming calcium oxide.
D. Calcium has a high electronegativity, so it gains electrons, resulting in a negatively charged ion. Oxygen has a low electronegativity, so it loses electrons, resulting in a positively charged oxide ion. The oppositely charged ions are attracted to each other, forming calcium oxide.