The correct order of radii is:

Explanation:
It is known that the size of isoelectron decreases with increase in atomc radius.
So, in option (B)  F, O2, N3 the all have same number of electrons but with the increase in atomic number, nuclear charge also increases.
Now, Fluorine has more ratio of nuclear charge per electron as compared to Oxygen.
So, nuclear charge increases as they are strongly bonded to the nucleus, decreasing the size of the atom.
So, option (B) is correct.
Final Answer:
Hence, option (B) is correct.