单项选择题
What qualities made the Silicon Valley impossible to clone?（）
A.Strong universities and a risk-taking culture B.Rich natural resource C.Residental circumstance and pleasant climate D.Reveloped economy
单项选择题 （）has the 19th-largest economy in the world.
单项选择题 What’s the meaning of “wax and wane” ?（）
判断题 When we land how can we get our stroller back?译文：等我们下机后, 我们怎样取回婴儿车呢?
