苏联解体的根本原因是：

A、长期以来体制上政策上的弊端和错误和积累

B、叶利钦长期的 * * 活动

C、戈尔巴乔夫推行错误的路线和政策

D、西方敌对势力长期推行“和平演变”战略

Mr Smith _____the grammar book meant for senior high school students and will almost finish it.[ ]

A. was writing  

B. has written  

C. has been written  

D. has been writing