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
网友回答
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。