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

 Progress ______ so far very good and we sure that the work will be finished on time.  

A. was         B. had been      C. has been     D. will be

 Edward, you play so well. But I        you played the piano.

A. didn’t know                                                     B. hadn’t known

C. don’t know                                                       D. haven’t known

 His sister left home in 1998, and        since.

A. had not been heard of                                        B. has not been heard of

C. had not heard of                                               D. has not heard of

 My parents have promised to come to see me before I                for Africa.

A. have left                B. leave                      C. left                       D. will leave