During the first simulation, approximately ___ of the radioactive atoms became stable after each half-life.

A. 100%

B. 50%

C. 25%

D. 10%

During the second simulation, approximately ___ of the radioactive atoms became stable after each half-life.

A. 100%

B. 50%

C. 25%

D. 10%

I'm not sure what do you mean by "first" and "second" simulation, however, the half-life of a radioactive element is the time after which 50% of the initial sample has decayed, and so it is the time after which 50% of the atoms have became stable.

So, the correct answer is B) 50%.