Identify the pair of elements in which the difference in atomic radii is maximum

Match the following.

List I (Element)	List II (Block)
A Ra	I p - block
B Uuq	II s- block
C Ds	III f - block
D Fm	IV d - block

The correct answer is

Identify the pair of element in which the number of $s$-electrons to $p$-electrons ratio is $2: 3$

Which of the following has the least electron gain enthalpy?