某物质沿曲线 <img src="https://static.zxtiku.com/wangke/imgs/topic/8dfddb8be5011a5d61b9c37beedafe20.jpg"/> 分布，其线密度为 <img src="https://static.zxtiku.com/wangke/imgs/topic/928c30d2a4310e084fe4992b65f96ab7.jpg"/>, 则其质量为<br /> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/08ef8e260cac8b1221934c9bf11f0c5c.jpg"/><br /> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/33377806c7eb913096dea45286993ca6.jpg"/><br /> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/94d660ea82befbab1a335015d1b1fc0f.jpg"/><br /> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/82ec8b7261e59cfad0c8e56ab7e0cd56.jpg"/>