问题补充：
—Where on earth have they gone?
—I have no idea, but I wish I .
A. know
B. knew
C. would know
D. would have known
答案：
A. know
(答案→)B. knew
C. would know
D. would have known
解析：虚拟语气题。Wish后的宾语从句用虚拟语气，对现在的希望从句谓语动词用过去是形式。 句意：他们到底去哪了？ 我不知道，但是我希望我知道。选B
