[单选题]
In radioactive dating, carbon-14 is often used. Thl ctn,. bdgve d -s,q8,7mhh5qis nucleus emits a single(ekh4/;x nj )j cyvqy* beta particle when )(c*/kyjnexv h jy; q4it decays. When this happens, the resulting nucleus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.
