选取长度相同的幼苗,实验装置如图甲所示,给予光照在不同时间测定幼苗伸长的长度,结果如图乙。能正确表示对照组、实验组向光侧和实验组背光侧幼苗伸长长度的曲线依次是( ) A . ①②③ B . ②③① C . ③②① D . ②①③ 答案:BWith April 18's railway speedup, highway and air transport will have to compete with _____ service for passengers.
[ ]A. good B. best C. better D. the best