22. On April 14, 2010, many people dressed in black with white flowers ______ their chests observed three minutes of silence in memory of the victims in Yushu Earthquake .

A. pinned in           B. pinned to        C. being pinned in      D. to be pinned to

23. The mayor of Zhuanghe City was ordered to resign because of his refusal to ________ when more than 1000 villagers got down on their knees before the city government office building, begging for his help.

A. break up          B. link up           C. fill up          D. show up 

24. After living in America for over 20 years, Brother Sway said to a reporter the other day, “I ________ done bigger things, had bigger achievements had I stayed in China.” .

A. must do           B. could do        C. could have done      D. must have done