问题补充:
The gap between rural and urban education in China is widening, and education is the key to rural problems.
A. solving
B. solve
C. have solved
D. having solved
答案:
(答案→)A. solving
B. solve
C. have solved
D. having solved
解析:考查非谓语动词。the key to……的关键,to为介词,故选A。