Final answer:
The element with an atomic mass number of 16 and an atomic number of 7 has 7 protons and 9 neutrons, corresponding to answer A.
Step-by-step explanation:
The element with an atomic mass number of 16 and an atomic number of 7 has 7 protons and 9 neutrons. The atomic number represents the number of protons in the nucleus, which in this case is 7. The mass number, which is 16, represents the total number of protons and neutrons.
By subtracting the atomic number from the mass number (16 - 7), we can find the number of neutrons, which is 9. Therefore, the correct answer is A. 7 protons and 9 neutrons.