—Have you ever visited the Water Cube? —Yes. When I served as a volunteer in Beijing, I      it twice.
#102056
A
have visited
B
visited
C
had visited
D
had been visiting
推荐题目
—When did you move to Qionghai?—In 2009.But I ________in Haikou for many years.
#99415
A
have worked
B
would work
C
have been working
D
worked
Residents ________ not to go out alone or to take part in any groups during the period of recent terrorist activities. 
#104240
A
were always being warned
B
are always warning
C
always warned
D
had always been warned
When she realized I _______ her, she quickly made a pose, smiling.
#103110
A
photographed
B
had photographed
C
was photographing
D
will photograph