[单选题]
In radioactive datingo4 rf+n0 1k v4viy-gpe, carbon-14 is often used.2ihq3ryk 3 uyw4lu 8y/ This nucleus emits a single beta party4 yu8y3/uq kw 2l3irhicle when it decays. When this happens, the resulting nucleus is
A. still carbon-14.
B. boron-14.
C. nitrogen-14.
D. carbon-15.
E. carbon-13.