Choice C. is equivalent.
Let's first simplify, starting with the denominator.
a to the power of 0 is 1. —> any value to the power of 0 is 1.
That leaves us with (1b^2)^4. Now we can distribute the exponent. But before that, let's get rid of the coefficient 1, which isn't necessary.
Now we are left with (b^2)^4.
Let's use the power of the power rule, which means that we multiply the exponent by the exponent. The denominator is now b^8.
Looking at the numerator, there is a b, which has a hidden exponent of one. —> We can get rid of it by taking away its exponent of 1 with the b^8 from the denomiator.
. . . b^1 goes away, and b^8 becomes b^7.
We cannot simplify any further, therefore the final expression is. . .
6a/b^7.