The train was traveling _____ forty kilometersan hour.(介词at

hey can sell their beef at a high price in the capital.介词at 后面常接表示花费、比率、程度、水平、年龄、速度等词,可以译作“以,用”.如：at a high price 意思是“以高价”,at a low cost 就是“以低成本”,We drove at high speed.我们以最高的速度开车.The train was traveling at 100 kilometers an hour.那火车以时速100公里行使.

at 速度、时间、程度都用at