Radioactive Decay: _{An Isotope of Tc Having a Half-Life of 6.0}

Multiple Choice

Radioactive decay: _{An isotope of Tc having a half-life of 6.0 h is used in bone scans. If a certain amount of this Tc is injected into the body, how long does it take for its initial decay rate to decrease BY 99%?}

A) (_{0.060 h})
B) (_{3.3 h})
C) (_{33 h})
D) (_{40 h})
E) (_{slightly more than a month})