John’sscoreonthetestisthehighestinhisclasshe___

John’s score on the test is the highest in his class, he ______ very hard.

A. must have studied

B. should have studied

C. must study

D. should study

正确答案：A
本题考查虚拟语气的用法根据题意：John的考试成绩是最高的故他肯定考试前努力了must+have+过去分词表示对过去的某事作出肯定语气的推测故选A