—What are you doing now, Lily?— I music.
A：am listening to
B：listen to
C：will listen to
—I think my Maths teacher is working hard. He teaches us very .
—Yes, but he can't come today. He doesn't feel .
6∶9和 16:19
口算．
453+198=____
10﹣0.03=____
0.1÷0.01=____
4×0.025=____
4.5﹣0.75=____
5×4÷5×4=____
3.14×1.6=____
28.26÷3.14=____
0.36+0.2=____
如图所示的四种实例中，属于光的直线传播现象的是（ ）
