Someone you adopt. Such as a foster parent, they are your guardian but not true parent. SO a foster someone you look after, even tho you arent their biological parent
The answer would be extra utility.
If the half-life is 5 minutes, then 30 minutes is equivalent to 6 half-lives. So, after six successive half-lives, the 400 mg of the radioisotope would have a mass of 400(0.5)⁶ = 6.25 mg.
Thus, A would be the correct answer choice here.
