—Must I finish the homework tonight?—No, you .You can finish it tomorrow.
A:mustn't
B:needn't
C:need
D:must
①顶点在圆周上的角是圆周角;②圆周角度数等于圆心角度数的一半;
③90°的圆周角所对的弦是直径;④圆周角相等,则它们所对的弧也相等.