从 A、B、C、D 四个选项中，选出可以填入空白处的最佳选项。
21. Great changes ______ in China in the past 20 years.
A. took place B. have taken place C. were taken place D. have been taken place
22. The manager meant ____ the workers that being 5 minutes late meant ____ the company.
A. to tell, to leave B. telling, leaving C. to tell, leaving D. telling, to leave
