What is the ground-state electron configuration of gallium (Ga, atomic number 31) using noble-gas shorthand?

• A. $\left[Ar\right]4^{s}23^{d}104^{p}1$
• B. $\left[Ne\right]3^{s}23^{p}64^{s}23^{d}104^{p}1$
• C. $\left[Ar\right]4^{s}23^{d}94^{p}2$
• D. $\left[Kr\right]4^{d}105^{s}25^{p}1$

Answer: (A)