Because we know that the half-lives of many radioactive isotopes are millions of years, we can deduce that
A) the longer it exists the more radioactive nuclei Earth produces.
B) the sun is the source of all the radioactive nuclei on Earth.
C) there must have been many more radioactive nuclei on Earth when life began.
D) there must have been far fewer radioactive nuclei on Earth before life began.
E) the natural radioactivity of minerals on the Earth was created by the Earth's internal temperature.

Question

Quizplus · Accepted Answer

The long half-lives of radioactive isotopes imply that they decay slowly over time. Therefore, if these isotopes are present now, there must have been a larger quantity of them in the past, including when life began on Earth.

Because We Know That the Half-Lives of Many Radioactive Isotopes