Write the Word or Phrase That Best Completes Each Statement $\mathrm { A } ( \mathrm { t } ) = \mathrm { A } _ { 0 } \mathrm { e } ^ { \mathrm { kt } } , \mathrm { A }$

Multiple Choice

Write the word or phrase that best completes each statement or answers the question.
-In the formula $\mathrm { A } ( \mathrm { t } ) = \mathrm { A } _ { 0 } \mathrm { e } ^ { \mathrm { kt } } , \mathrm { A }$ is the amount of radioactive material remaining from an initial amount $\mathrm { A } _ { 0 }$ at a given time $t$ , and $\mathrm { k }$ is a negative constant determined by the nature of the material A certain radioactive isotope decays at a rate of $0.225 \%$ annually. Determine half-life of this isotope, to the nearest year.

A) $308 \mathrm { yr }$
B) $134 \mathrm { yr }$
C) $222 \mathrm { yr }$
D) $3 \mathrm { yr }$