这20年间，世界发生了翻天覆地的变化。时而波澜壮阔，令人振奋；时而风雨如磐，惊心动魄。

　　A. Over the past 20 years, the world has changed greatly. It is sometimes sweeping inspiring it is sometimes stormy disquieting.

　　B. Over the past 20 years, the world has witnessed great changes which are sweeping inspiring at times stormy disquieting at others.

　　C. Over the last 20 years, the world has changed greatly, sometimes sweepingly inspiringly sometimes stormily disquietingly.

　　D. Over the last 20 years, the world has witnessed great changes, at times sweepingly inspiringly at others stormily disquietingly.