已知抛物线y2=6x的焦点为F,点A(0,-1),则直线AF的斜率为( )
A <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184336_3060.png" width="18" height="37" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184340_5092.png" width="40" height="37" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184343_9935.png" width="40" height="38" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/20190817184347_7435.png" width="18" height="38" />