在产销平衡运输问题中，设产地为 m个，销地为n个，那么基可行解中非零变量的个数  

A、<span style="TEXT-DECORATION: none"><span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px; TEXT-DECORATION: none">不能大于</span><span style="FONT-FAMILY: &#39;Times New Roman&#39;,&#39;serif&#39;; FONT-SIZE: 14px; TEXT-DECORATION: none">(m+n-1)</span></span>

B、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">不能小于</span><span style="FONT-FAMILY: &#39;Times New Roman&#39;,&#39;serif&#39;; FONT-SIZE: 14px">(m+n-1)</span>

C、<span style="FONT-FAMILY: 宋体; FONT-SIZE: 14px">等于</span><span style="FONT-FAMILY: &#39;Times New Roman&#39;,&#39;serif&#39;; FONT-SIZE: 14px">(m+n-1)</span>

D、<p style="LINE-HEIGHT: 150%"><span style="FONT-FAMILY: 宋体">不确定</span></p><p></p>