The population of Africa is so rapidly as to cause concern of the whole world.A. expandin

问题补充：

The population of Africa is so rapidly as to cause concern of the whole world.

A. expanding

B. circulating

C. exporting

D. spreading

答案：

(答案→)A. expanding

B. circulating

C. exporting

D. spreading

解析：动词辨析。句意：非洲人口在快速增长，引起了世界的关注。expand：扩张、发展；circulate：循环；export：出口；spread：扩散。