Select the coorect statement regarding Slater rules .
A. `Z_(eff)` on 4s electron is more than 3d electron bacause it is filled completelty before 3d
B. In P atom ,1s electrons are more shielded than 2p electros
C. In Zn atom ,3d electrons provide effective shielding to 3s electrons
D. In Zn ,`Z_(eff)` on 3s and 3p electron is equal