I______tothelecturethatafternoon,butI______abitill.
A.should have gone; wasB.would have gone; had beenC.should go; wasD.would go; had been在线课程A
解析：
考查虚拟语气。根据时间状语that afternoon可知是对过去的情况比赛虚拟，使用情态动词+have done,排除CD。Should have done本应该做某事，实际上却未坐；would have done会做某事。But后面的句子应该使用陈述语序，根据前句的that night可知后半句使用过去时。故A正确。