行包快运专列专用车辆的有调中转作业为20min。
参考答案:错
大树底下好乘凉说明______;仙人掌的叶变成刺状说明______.
All of the flowers now raised here have developed from those _____ in the forest. [ ]
A. once they grew
B. they grew once
C. they once grew
D. once grew