He witnessed Yushu, a county in Qinghai Province hit by _____ unexpected earthquake, but the Yushu people haven’t lost heart, vowing to turn their homeland into _____ more beautiful Yushu.

A．a; a

B．an; the

C．the; a

D．an; a

排列图法是利用排列图寻找工程质量主次问题的一种有效方法，实际应用中，通常按累计频率划分为( )。

A．0～60%

B．0～80%

C．60%～90%

D．90%～100%

E．80%～90%