Screening effect influences
A) atomic radius
B) ionisation enthalpy
C) electron gain enthalpy

screening effect is inversely proportional to effective nuclear charge.

Higher the effective nuclear charge lesser the atomic radii because more the charge ,more heavily the electron is attracted towards the centre and lesser is the size.

Ionisation energy is directly proportional to effective nuclear charge because if a nuclear has a higher force of attraction towards its valence electrons, so it binds electrons very well and it will be difficult to remove them, so higher energy will be required to remove them.

We know that as effective nuclear charge increases electron gain enthalpy decreases.

Therefore, option(d) is the answer.