Ireland is unique among European countries for _______.

Ireland is unique among European countries for _______.
A、its small population
B、its beautiful scenery
C、its rich natural resources
D、its century-long population emigration
【正确答案】：D
【题目解析】：爱尔兰在欧洲国家中是独一无二的，因为其长达一个世纪的人口迁移。