Final answer:
The anion formed from an oxygen atom is called an oxide ion, which is formed when oxygen gains two electrons to achieve a stable configuration. Therefore, the correct option is B.
Step-by-step explanation:
The anion formed from an oxygen atom is called the oxide ion. Anions are negative ions, and in the case of oxygen, it typically gains two electrons to achieve a stable electron configuration, similar to that of the noble gas neon. When naming monatomic anions, the stem of the element is used with the suffix '-ide' added, followed by the term 'ion'. Thus, the correct name for the oxygen anion is 'oxide ion', denoted as O²⁻.