I think the correct answer would be none of the choices. After one half-life, 50 percent of the original would remain. Then, after two half lives, 25 percent would only remain. Also, after three half lives, only 12.5% would remain of the original amount. And, after four half-lives, 6.25% of the original will remain. From the choices, none of those are correct. Half life is the time needed for a certain amount of a substance to be reduced into half the initial amount. It a term commonly used in nuclear chemistry and is commonly associated with radioactive substances and radioactive decay.
