The correct option is D 199F and 136C
Isodiaphers are species with different atomic numbers and mass numbers, but with the same number of neutrons in excess.
199F and 136C have different atomic numbers and different mass numbers.
Calculating the difference (n – p),
Number of neutrons (n) in 199F= 19 – 9 = 10, number of protons (p) = 9 So,
n – p = 1
Number of neutrons (n) in 136C = 13 – 6 = 7, number of protons (p) = 6. So,
n – p = 1