Now more and more workers ______their free time trying to improve themselves at school or college.
A:take
B:cost
C:spend
D:pay
①地球是圆形 ②地球是球体
③地球的平均半径是6371千米 ④地球的最大周长约为5.1万千米
统治时期,人口增长,边疆巩固开拓,史称有“贞观遗风”,为唐朝全盛时期到来奠定基础的皇帝是( )