C-14 has a half life if approximately 5700 years how many years will it take for the radioactivity of a sample to reach one-fourth of its original amount

A. 1425

B. 5700

C. 11400

D. 22800

This is an easy half-life problem.

Every half-life, a substance loses half its radioactivity. So, after 2 half-lives, a substance will have a quarter of its radioactivity.

2 * 5,700 = 11,400 years

answer is C