单选题 It is absolutely imperative that governments of all levels______on this issue in spite of some difficulties.
【正确答案】 C
【答案解析】解析：句意：尽管有一些困难，各级政府必须就此问题进行合作。It is imperative that后面要接虚拟语气，因此这里要用省略should的动词原形。