[单选题]
A neutral atom has an eleayumxp9 y 1dl7l,0cgs99 l tt+ctron cong1b a3/banjk+1qhjp19aop, 1a i , hmgfiguration of $1s^22s^22p^6$. If a neutral atom holds one additional electron, what is the ground state configuration?
A. $1s^22s^22p^63s^1$
B. $1s^22s^22p^7$
C. $1s^22s^32p^6$
D. none of the given answers