L是抛物线<img src="https://static.zxtiku.com/wangke/imgs/topic/18fc07387ece91ed6510618d012fdea9.jpg"/>自点<img src="https://static.zxtiku.com/wangke/imgs/topic/fc085486fc023a9d2af7b92a098362d2.jpg"/>至点<img src="https://static.zxtiku.com/wangke/imgs/topic/30f47fa83ff2197f79d8cc065042284a.jpg"/>的弧段，计算<img src="https://static.zxtiku.com/wangke/imgs/topic/0dc5a67ac1a74702213b459716a8d6b7.jpg"/>( ) A. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/d7be815a12a0206f12c78d34c5ccff90.jpg"/> B. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/80b60fe4960a086d15a25cabda63bfe6.jpg"/> C. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/12f5ee3337cda31642927e9a1a8932ee.jpg"/> D. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/282432fbaa4106c4e0825ae071c2bf7a.jpg"/>