When dividing exponents with the same base, you must subtract the second exponent from the first:
[tex]\frac{10^{12}}{10^{-3}}[/tex]
= [tex]10^{12 - (-3)}[/tex]
= [tex]10^{12 + 3} [/tex]
= [tex]10^{15} [/tex]
So D is the correct response. Hope this helps! :)