Answer:
Option A. 10 years
Step-by-step explanation:
we know that
Half-life [tex](t^{\frac{1}{2}})[/tex] is the amount of time required for a quantity to fall to half its value as measured at the beginning of the time period.
In this problem [tex](t^{\frac{1}{2}})[/tex] of a radioactive isotope is 10 years, which means that after 10 years half of the sample would have decayed and half would be left as it is.
After 10 years ( first half life) 5/2 = 2.5 g decays and 2.5 g remains left
