[单选题]
In radioactive dating, m-b leb he ah+ e0(ga(24;rdmrcarbon-14 i j*zy/3r)vw hps often used. This nucleus emits a single beta particle when it decays. When this happens, the resulting nhpv/yz3* )rjwucleus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.
