问题补充:
To prepare for the Olympic Games in summer, London its largest ever exercise to test the response of emergency services.
A. planned
B. is planning
C. had planned
D. plans
答案:
A. planned
(答案→)B. is planning
C. had planned
D. plans
解析:考查时态。根据句意:为了准备今年夏天的奥运会,伦敦正在计划一个有史以来最大的锻炼来检查对紧急服务的回应。