¡¡¡ ! i'm stuck on a question.. a sample contains 4.0 mg of uranium-238. after 4.46×10^9 years the sample will contain 2.0 mg of uranium-238. what is the half life of uranium-238?

 The half  life  of uranium- 238  is

 4.46 x10^9  years

 Explanation

Half life  is the time  taken for  the  radioactivity  of   a isotope  to fall  to half  its  original  value.

The  original   mass  of uranium-238  is  4.0 mg

  Half  of original  mass of uranium  = 4.0  mg /2 = 2.0  mg

since  it  take 4.46  x 10^ 9 years  for  the sample   to half  the half life of uranium -238 = 4.46 x10^9 years

i think it's letter a.