To find the point that lies on the graph of the logarithmic function \( g(x) = \log_9 x \), we can utilize the relationship between exponential and logarithmic functions.
Given that \( f(x) = 9^x \) includes the point \( (2, 81) \), we can express this as:
\[ f(2) = 9^2 = 81 \]
Now, the logarithmic function \( g(x) = \log_9 x \) gives us the relationship where:
\[ g(81) = \log_9 (81) \]
Since \( 81 \) can be rewritten as \( 9^2 \), we find:
\[ g(81) = \log_9 (9^2) = 2 \]
Thus, the point \( (81, 2) \) lies on the graph of the logarithmic function \( g(x) = \log_9 x \).
So, the correct response is:
\[ \text{(81, 2)} \]