Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
-A certain radioactive isotope has a half-life of approximately 1250 years. How many years to the nearest year would be required for a given amount of this isotope to decay to $70 \%$ of that amount?

A) $375 \mathrm { yr }$
B) $2171 \mathrm { yr }$
C) $573 \mathrm { yr }$
D) $643 \mathrm { yr }$