A:θ-π2
B:π2+θ
C:3π2-θ
D:θ
This big bag is too heavy for the little boy ______.Who volunteers to help him?
如图所示,是声音输入到示波器上时显示振幅与时间关系的波形.其中声音音调相同的是 ____图和 ____图,响度相同的是 ____图和 ____图.