By the time you arrive this evening,____ for two hours.A.I will studyB.I will have been studiedC.I had studiedD.I will have been studyingB和D区别在哪儿啊？
问题描述：
By the time you arrive this evening,____ for two hours.
A.I will study
B.I will have been studied
C.I had studied
D.I will have been studying
B和D区别在哪儿啊？
答