The atomic number of beryllium is 4. The mass number of a beryllium atom is 9.
Which row in the table shows the number of protons, neutrons, and electrons in a neutral atom of beryllium-9?
| Row | Protons | Neutrons | Electrons |
|---|---|---|---|
| A | 4 | 4 | 5 |
| B | 4 | 5 | 4 |
| C | 5 | 4 | 9 |
| D | 9 | 5 | 4 |
Row A
Row B
Row C
Row D
