请教单选题，谢谢！1.There_________alotofd
1.There _________a lot of difficulty in finishing the ta on time ,doesn"t there? A.exists B.is C.used to be D.must be 2.There must exist some misunderstanding between you and Bob of this problem,________? A.mustn"t there B.aren"t you C.is
1.a,exists是第三人称单数，对应does 2.d，must表示推测,exist对应does