问题补充:
----- Have you ever visited the Shanghai World Expo?
-----Yes.When I was in China , I it twice.
A. have visited
B. visited
C. had visited
D. would visit
答案:
A. have visited
(答案→)B. visited
C. had visited
D. would visit
解析:考查时态。句意:你曾经参观过的上海世博会吗?——是的。当我在中国时,我参观过两次。可知下文描述的是在过去某个时间发生的动作,故用过去时态。选B。