The Radioactive Isotope Bismuth-210 Has a Half-Life of 5 Days $t$

Multiple Choice

The radioactive isotope Bismuth-210 has a half-life of 5 days. Suppose we have an initial amount of 100 mg. The amount of Bismuth-210 remaining after $t$ days is

A) $100 \left( 2 ^ { 0.2 t } \right)$
B) $5 \left( 2 ^ { 0.2 t } \right)$
C) $50 \left( 2 ^ { - 0.2 t } \right)$
D) $100 \left( 2 ^ { - 0.2 t } \right)$
E) $100 \left( e ^ { 0.2 t } \right)$
F) $5 \left( e ^ { 0.2 t } \right)$
G) $50 \left( e ^ { - 0.2 t } \right)$
H) $100 \left( e ^ { - 0.2 t } \right)$