[单选题]
The elements in the periodic tabl0rtvpqnst9dow) (xt k/x;xxx5vpl 07 9b. 8 sae which have a1*uy;rr4 rbg rkn8(iu single outer s electron are referred ton; k 1b*ug(rrrry8 ui4 as
A. noble gases.
B. halogens.
C. alkali metals.
D. transition elements.