2 83. The base of a solid is the region bounded by a portion of the graph of y = sin (플 x and the x-axis, as shown in the figure above. For the solid, each cross section perpendicular to the x-axis is a rectangle of height 3. Which of the following expressions gives the volume of the solid? (A) (B) (C) * 3 sin (4x) dx S ² 3 sin ² (1-x) dx L² 3x sin ( x ) dx (D) S 3x sin² (x) dx