佛劳得数是 A. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/6cf07ba0c26f6d564851bfc46ddbcf5c.jpg"/> B. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/6e0b8f9193a1a9386bc545f6969a3c60.jpg"/> C. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/1f91dda5077f07c0924cfa64a6c606c9.jpg"/> D. <br/> <img src="https://static.zxtiku.com/wangke/imgs/topic/bb42c331440de8405eb907ce83138f4c.jpg"/>