The population of Rui’an is so rapidly as to cause concern of the whole country.A. expand

问题补充：

The population of Rui’an is so rapidly as to cause concern of the whole country.

A. expanding

B. exploring

C. extending

D. spreading

答案：

(答案→)A. expanding

B. exploring

C. extending

D. spreading

解析：本题考查动词辨析。expand不仅指尺寸的增加，还可指范围和体积的扩大。stretch一般指由曲变直、由短变长的伸展；extend指空间范围的扩大或长宽的向外延伸，也可指时间的延长；spread一般指向四面八方扩大或传播。