Use the Pythagorean theorem to find the length of the trail segment (the hypotenuse).

Use $\sin\theta=\frac{\text{opposite}}{\text{hypotenuse}}$ and simplify the fraction.

In Desmos, enter sqrt(9^2+12^2) to compute the hypotenuse length.

Enter 9/(sqrt(9^2+12^2)) to compute $\sin\theta$.

Convert the result to an exact fraction (or simplify $\frac{9}{15}$) and select the matching option.

The vertical rise and horizontal run are the legs of a right triangle, so the hypotenuse is

Here, $\sin\theta=\frac{\text{opposite}}{\text{hypotenuse}}=\frac{9}{15}=\frac{3}{5}$.

So the correct choice is $\frac{3}{5}$.