Moving from Left to Right Across the Periodic Table, the Atomic

Multiple Choice

Moving from left to right across the Periodic Table, the atomic radii of the first row transition elements does not show the same trend as the s and p blocks, e.g. from lithium to fluorine. Why?

A) d electrons screen more effectively than s and p electrons, so Z_eff falls.
B) The increase in the electron-electron repulsion becomes more important as the d orbitals are filled and counteracts the effect of the increase in Z_eff.
C) d electrons screen less effectively than s and p electrons, so Z_eff rises.
D) Z_eff is unaffected by the increasing number of electrons as d electrons screen so poorly.