[单选题]
In radioactive dating, carbon-14 is9 3krkjr4 l,lk often used. This nucleus emits .gx0a g fmo1reu1ai3-edp,s: a single beta particle when it decays. When this happens, the resu11,grs3mg:e 0dxiopa.-euf a lting nucleus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.