The atomic radius of elements of which of these would be nearly same?
Na, K, Rb, Cs
F, Cl, Br, I
Li, Be, B, C
Fe, Co, Ni, Cu
As we have learnt,
Atomic radii of transition elements remain almost same in a period. Therefore Fe, Co, Ni, Cu have nearly same atomic radii.
Hence, option number (4) is correct