The correct answer is B. It's because the result of dividing exponentations with the same bases (other than 0) is always the same base powered to the difference of all the exponentations. The formula is:
[tex]\frac{a^{n}}{a^{m}} = a^{n - m}[/tex]
In this situation it's:
[tex] \frac{7^{3}}{7^{5}} = 7^{-2}[/tex] because 3 - 5 = -2.
