见面课：话题讨论：美国国家公园体系带给我们的启示
What’s the meaning of “wax and wane” ?兴衰成败
__ has the 19th-largest economy in the world.The Bay Area
What qualities made the Silicon Valley impossible to clone?Strong universities and a risk-taking culture
Many startups in Silicon Valley are branching out into new places that the trend has a name, Off Silicon Valleying.对
If you husband something valuable, you use it _____ .Carefully