unit 3 travel journal 单元自测 （模块） 1完形填空 阅读下面短文，掌握其大意，然后从21—30各题所给的a、b、c和d项中，选出最佳选项，并在答题卡上将该项涂黑。字数：217 完成时间：15分钟 难度：*** when it’s 10:15 in new york, it’s 9:15 in salt lake city, and 7:15 in san francisco – isn’t it? this consistent and orderly time system, based on a grid of time 21 , seems so natural that people 22 give it a moment’s thought. so you may find it surprising to learn that prior to the late 1800s each community 23 its own time – by looking at the sun. when the sun shone directly overhead in washington, d.c., for example, it was 12:00 noon there; up the road in philadelphia,
