1. Boulder was one of the first cities in the nation to enforce a ban on smoking. 博尔德是该国率先施行禁烟令的城市之一。
2. Given enough warning, it should be possible to push a threatening boulder out of the way. 如果予以足够的警示，就有可能把一块有威胁性的巨石推开。
3. Once you have started the boulder rolling, it develops momentum, which is defined by its mass and velocity. 一旦你开始让巨石滚动，巨石就会产生动量，这是由其质量和速度决定的。
4. Similar measures in California's Albany, Oakland, San Francisco and Colorado's Boulder are becoming hot-button issues. 加州奥尔巴尼、奥克兰、旧金山和科罗拉多州博尔德的类似措施正成为热点问题。
5. As with Sisyphus, the boulder was painstakingly rolled upwards only to tumble back down again in an absurd exercise of futility. 和西西弗斯一样，巨石费力地向上滚动，结果又滚了下来，徒劳无功。
