Explanation
For any given angle in a right triangle that is not the 90° angle its sine is given by the quotient between its opposite side and the hypotenuse. For triangle ABC the hypotenuse is BC and the opposite side to theta is AB. Then the sine of this angle is given by the following equation:
[tex]\sin\theta=\frac{AB}{BC}=\frac{4}{5}[/tex]Answer
Then the answer is the third option, 4/5.
