[单选题]
In radioactive dating, carbon-14 is o0oi 1wi63jfwd uv(zm- ften used. This nuclemrxq60d2-3vkbu i+czx.r,u n/7j ru gus emits a single beta particle when it decays. When t x gj3d+ui7/6m2, vr bc.rrqzkxnuu-0his happens, the resulting nucleus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.
