Atomic mass of oxygen is

Explanation: Oxygen has an average atomic mass of 15.9994 atomic mass units which are generally mentioned as 16 amu. This atomic mass, on the other hand, is the average atomic mass of all isotopes in nature. As a result, the first isotope is more prevalent. When there is a mention of an oxygen atom then it refers to the oxygen having eight neutrons.

Final answer: Thus, Option B is the correct answer. Atomic mass of oxygen is 16 u.