已知平面区域D由以A(1,3),B(5,2),C(3,1)为顶点的三角形内部以及边界组成.若在区域D上有无穷多个点(x,y)可使目标函数z=x+my取得最小值,则m=( )
A.-2
B.-1
C.1
D.4
0 90562 90570 90576 90580 90586 90588 90592 90598 90600 90606 90612 90616 90618 90622 90628 90630 90636 90640 90642 90646 90648 90652 90654 90656 90657 90658 90660 90661 90662 90664 90666 90670 90672 90676 90678 90682 90688 90690 90696 90700 90702 90706 90712 90718 90720 90726 90730 90732 90738 90742 90748 90756 266669
A.-2
B.-1
C.1
D.4