如图所示为垂直于线圈平面通过的磁通量，它随时间变化的规律为<img src="https://static.zxtiku.com/wangke/imgs/topic/11e318628b1fe46427c8629a09369c03.jpg"/>，式中<img src="https://static.pphuashu.com/wangke/imgs/topic/6c62cbf77cd5b0e04ef0976001737705.jpg.png"/>的单位为mWb。试问当<img src="https://static.zxtiku.com/wangke/imgs/topic/f4e5a0cc94e42c571475dc2d291b482f.jpg"/>时，线圈中的磁感应电动势为( )mV。<br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/e9b9bb2450e5593f29b5cf79e7d7bc0b.jpg"/> A. <br/> 21 B. <br/> 31 C. <br/> 41 D. <br/> 51