Simplify:

(3a^2 b)^2 (ab)^3

A. 6a^7 b^5
B. 9a^12 b^6
C. 9a^7 b^5
D. 6a^12 b^6

To simplify, you need to multiply the exponents of the same variables and then multiply the numerical coefficients:

(3a^2 b)^2 (ab)^3 = 9a^4 b^2 * a^3 b^3

Now, you can combine the exponents of the same variables:

9a^4 b^2 * a^3 b^3 = 9a^(4+3) b^(2+3) = 9a^7 b^5

So, the simplified expression is 9a^7 b^5.

The correct answer is C. 9a^7 b^5.