Screening of the Nuclear Charge by Core Electrons in Atoms

Screening of the nuclear charge by core electrons in atoms is ________.

A) less efficient than that by valence electrons
B) more efficient than that by valence electrons
C) essentially identical to that by valence electrons
D) responsible for a general decrease in atomic radius going down a group
E) both essentially identical to that by valence electrons and responsible for a general decrease in atomic radius going down a group