The "Third-Life," the Time It Takes Nuclei to Decay Until $\beta$

Multiple Choice

The "third-life," the time it takes nuclei to decay until one-third of the original amount remains,expressed in terms of the decay constant $\beta$ ,is

A) (ln 2) /3 $\lambda$
B) (ln 3) / $\lambda$
C) (ln 0.333) / $\lambda$
D) 3(ln 2) / $\lambda$
E) $\lambda$ /3