In the Bohr model, you can see that p corresponds to "protons" and n corresponds to "neutrons".
You can see in the periodic table that the atomic number which is the same as the number of protons for fluorine is 9. So, p = 9.
The electrons are the little circles in the orbits of the Bohr model, so it must be 9 electrons because they're telling us that fluorine is stable.
And to find the number of neutrons, you can see that the number that is beside fluorine-19 is 19. This number represents an isotope and using this number to calculate the number of neutrons is resting this value by the number of protons (9). So, the number of neutrons would be n = 19 - 9 = 10.
The answer would be B because in the last orbital must be seven electrons because fluorine contains seven electrons of valence (you can see this watching the number of columns in the periodic table: fluorine is in the family VII A, so it has 7 electrons in their last orbital).