interval histogram

例句：

1. 1. The interval betweenclasses is 30 minutes.
   课间休息是30分钟。
2. 2. Theinterval between the two eventswas only a few hours.
   两个事件之间的间隔只有几个小时。
3. 3. The intervalbetween the start and end of the raceis 45 minutes.
   比赛开始和结束之间的间隔是45分钟。