单选20．流程工业中，为协调前后工序的物料流量而提出的控制策略是（   ）

A、<span style="font-size:16px;font-family:宋体">前馈控制</span><span style="font-size: 16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp;&nbsp;</span>

B、<span style="font-size:16px;font-family:宋体">选择性控制</span><span style="font-size: 16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp; &nbsp;</span>

C、<span style="font-size:16px;font-family:宋体">分程控制</span><span style="font-size: 16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;">&nbsp; &nbsp;&nbsp;</span>

D、<span style="font-size:16px;font-family:宋体"></span><span style="font-size:16px;font-family:宋体"></span><span style="font-size:16px;font-family:宋体">均匀控制</span><span style="font-size:16px;font-family:&#39;Times New Roman&#39;,&#39;serif&#39;"></span>