his average speed had been 299 miles per hourhad been 是什么?

His average speed had been 301 miles per hour.句子成分 英文数学题Ben cycles to a city at average speed X and returns at average speed Y.His average speedfor the whole trip is ( ) his average speed had been 299 miles per hourhad been 是什么? Campbell was disappointed to learn that his average speed had been 299 miles per hour.句子成分 average extruding speed 怎么翻译 average velocity和average speed区别在哪? his average speed had been 299 miles per hour这句话用的是过去完成被动时态吗 为什么要用被动形式呢? A speed relative to average reading speed=1.2什么意思到底是A快还是average reading speed快?A是average reading speed的1.2倍还是average reading speed是A的1.2倍?换言之,如果A speed relative to average reading speed=0.9是否说,A average speed 和average velocity 有什么区别?不要解释的太复杂.简单点就好. However,a few days later,he was told that a mistake had been made.His average speed had been 301 miles per hour.为什么不用过去式?was made、 was 301 miles per hour? his average speed had been 301 这里面的been是什么我知道是过去完成时 但我就是不知道为什么要加been 我不能当成被动句 又不能译作完成进行时 此文中第一句句子为什么不用过去完成时?Although Campbell reached a speed of over 304 miles per hour,he had great difficulty in controlling the car .Campbell was disappointed to learn that his average speed had been 299 miles per hour. Ali drove from Town A to Town B at an average speed of 60 km/h.He took 1 hour and 20 minutes to reach Town B.If he were to increase his speed by 20%,how much time would he save?给个翻译和答案,please. Ali drove from Town A to Town B at an average speed of 60 km/h.He took 1 hour and 20 minutes to reach Town B.If he were to increase his speed by 20%,how much time would he save?给个翻译和答案,please. average average average average