【题目】I ________________ in the exam, but I was too careless.
A.should have been carefulB.must have been careful
C.should be carefulD.must have been careful
在线课程【答案】A
【解析】
考查情态动词+have done的用法。句意：我本应该在考试时仔细点，但是我太粗心了。结合语境可知，此处是虚拟语气，考查should have done本该做某事（事实上没做），故选A项。