[单选题]
In radioactive dating, carbon-14 isd8xk ) *m-yn.wd3wsfj often used. r.z/ lc vjpg9,This nucleus emits a single beta particle when it decays. When this happens, the resulting nuclel.rgj9cp/v ,zus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.