Which of the following correctly used the Power Rule of Exponents in the expression (10^9)7?

90^7

10^63

10^2

10^16

The correct answer is 10^63.

According to the Power Rule of Exponents, (a^m)^n = a^(m*n).

In the given expression, (10^9)^7, m = 9 and n = 7.

Therefore, (10^9)^7 = 10^(9*7) = 10^63.

The correct usage of the Power Rule of Exponents in the expression (10^9)7 is 10^63.