Over the past decades, sea ice in the Arctic as a result of global warming.
A. had decreased B. decreased C. has been decreasing D. is decreasing
During the period of recent terrorist activities, people _______ not to touch any unattended bag.
A. had always been warned B. were always being warned
C. are always warning D. always warned
Mary went to the box office at lunch time, but all the tickets ______ out.
A. would sell B. had sold C. have sold D. was selling
This is the first time we______ a film in the cinema together as a family.
A. see B. had seen C. saw D. have seen
My parents _____ in Hong Kong. They were born there and have never lived anywhere else.
A. live B. lived C. were living D. will live
I was out of town at the time, so I don’t know exactly how it _______.
A. was happening B. happened C. happens D. has happened
