Lanthanoid contraction is caused due to:

Options

A. the appreciable shielding on outer electrons by `4f` electrons from the nuclear charge
B. the appreciable shielding on outer electrons by `5f` electrons from the nuclear charge
C. the same effective nuclear charge from `Ce` to `Lu`
D. the imperfect shielding on outer electrons by `4f` electrons from the nuclear charge

Answer

D

Explanation

Lanthanoid contraction is due to ineffective shielding produced by larger `f`-subshell.