问题补充：
Do you know how many people up to now?
A. have invited
B. have been invited
C. had invited
D. had been invited
答案：
A. have invited
(答案→)B. have been invited
C. had invited
D. had been invited
解析：up to now 直到现在，应用现在完成时，进一步分析many people和invite之间是被动关系，应用现在完成时的被动语态：have/has been done 本题大意，你知道，到现在为止，有多少人被邀请了吗？
考查点：现在完成时的被动语态
