with ()reform over the past twenty years为什么括号里填economic呢?

with ()reform over the past twenty years为什么括号里填economic呢? over the past twenty years 还是in the past twenty years In the past twenty years,Lau has made over one hundred films over the past ten years 为什么是in the past three years而不是over the past three years over the past ten years是什么意思 Over the past fifty years,young The past twenty years witnessed the fast development of the Many changes_____(take)place over the past ten years/ 填什么? 英语翻译The past twenty years witnessed the fast development of Over the past ten years ,over这里是介词吗 （）climb over the fence. 括号里填什么