SAT Question 87a9a2d4: Right Triangles And Trigonometry answer and explanation with Desmos solution

Choice B is correct. The sine of an acute angle in a right triangle is the ratio of the length of the side opposite that angle to the length of the hypotenuse. The hypotenuse of a right triangle is the side opposite the right angle. In right triangle $ABC$, side $BC$ is the side opposite angle $A$ and side $AB$ is the hypotenuse. It's given that the length of side $BC$ is $35$ units and the length of side $AB$ is $171$ units. Therefore, the value of $\sin A$ is $\frac{35}{171}$.