—Students are supposed _______.
—I agree with you.
A:study hard
B:studying hard
C:to studying hard
D:to study hard
某同学在做“用电压表和电流表测灯泡的电阻”实验时,连接电路如图所示.请指出他的接线中的错误,应如何纠正?
—I agree. Trees are getting now.
当我们的手无意中碰到高温物体时,会立即缩回来,这个过程称为缩手反射.它由如图所示的反射弧来完成.其中手部皮肤属于( )