It is desirable that the automation equipment-running as muc

It is desirable that the automation equipment_running as much of the time as possible.
A.would be kept B.must be kept C.will be kept D.should be kept

D正确.

解释：
这是一种虚拟语气.语法规则如下：
It is/was desirable (important, essential, necessary, advisable, imperative, obligatory, preferable, natural, vital, 等形容词) 后面是that 从句时,从句中的谓语动词常用 should + 动词原形.其中should 可以省略.这类形容词通常表示“建议”或“有必要”.