―Congratulations, Jane, you have won the first prize in the physics competition.

―Thank you, Mr Green. I can’t make such great __________ without your help.

A．experience

B．experiment

C．progress

D．operation

一只矩形线圈匀强磁场中绕垂直于磁场的轴匀速转动穿，过线圈的磁通量随时间变化的图象如图中甲所示，则下列说法中正确的是（　　）

A．t=0时刻线圈平面与中性面垂直

B．t=0.01s时刻，Φ的变化率达最大

C．t=0.02s时刻，交流电动势达到最大

D．该线圈相应的交流电动势图象如图乙所示