After three half-lives have elapsed, what fraction of the original amount of radionuclide remains? 1/3
1/4
None of these
1/8

b is the correct

i don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.

6.4 cm (max) - 25 cm (min)