Use the unit circle, along with the definitions of the circular functions, to find the exact values for the given functions when $s=-\pi$. Select the correct choice below and fill in any answer boxes in your choice. A. $\sin (-\pi)=$ (Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.) B. The solution is undefined.

Step 1 ：The sine function, \(\sin(x)\), gives the y-coordinate of the point on the unit circle that is \(x\) radians counterclockwise from the point (1,0). When \(x=-\pi\), this corresponds to the point on the unit circle that is \(\pi\) radians clockwise from the point (1,0), which is also the point (1,0). Therefore, \(\sin(-\pi)\) should be the y-coordinate of this point, which is 0.

Step 2 ：The result from the calculation is extremely close to 0, but not exactly 0 due to the limitations of precision in calculations. However, mathematically, the exact value of \(\sin(-\pi)\) is 0.

Step 3 ：Final Answer: \(\sin (-\pi)= \boxed{0}\)