similar measures in California's Albany, Oakland, San Francisco and Colorado's Boulder are becoming hot-button issues health advocacy groups have hinted that even more might be coming.
2019年12月四級(jí)真題（第一套）閱讀 Section C
Once you have started the boulder rolling, it develops momentum, which is defined by its mass and velocity.
出自-2015年12月閱讀原文
If you try to push a boulder ( ' , 大圓石 ), it pushes you bock.