A high official from the central government will come and explain what the country has do

问题补充：

A high official from the central government will come and explain what the country has done to ensure to make the Football World Cup the best-ever game.

A. in length

B. at length

C. by length

D. to length

答案：

A. in length

(答案→)B. at length

C. by length

D. to length

解析：短语辨析。A.长度 B. 最后；详细的 C. 按单位长度 D.按一定长度。句意：一位来自中央政府的高级关于要来详细解释国家为确保足球世界杯成为最好的一届做了些什么。故选B。