单选题
Three concentric circles centered at O have radii of 1, 2, and 3. Points B and C lie on the largest circle. The region between the two smaller circles is shaded, as is the portion of the region between the two larger circles bounded by central angle BOC, as shown in the figure below. Suppose the shaded and unshaded regions are equal in area. What is the measure of ∠BOC in degrees?
三个同心圆以 O 为圆心，半径分别为 1,2,3. 点 B 和 C 在最大的圆上。如下图所示，两个较小的圆之间的区域涂为阴影，两个较大的圆之间以圆心角
\( \angle BOC \)
为界的区域部分也涂为阴影。假设阴影区域和非阴影区域的面积相等。问
\( \angle BOC \)
的度数是多少？
A
108
B
120
C
135
D
144
E
150
答案与解析
答案：
A
解析：
