题目

They say there are three ways to experience the Grand Canyon(科罗拉多大峡谷): on foot, on mules (骡子) or by air. We chose the first. Up early, my husband and I and our three children couldn’t wait to get started. We decided to walk along a lovely path named Bright Angel Trail. As we set out, I was shocked at how narrow the path was. And I couldn’t help noticing that the other tourists weren’t like us. They had heavy backpacks, water bottles, and hats. But as usual we were dressed. As the sun rose higher, Arizona’s famous heat seemed to roast (烘烤) us. There was no已知卤代烃可以和钠发生反应，例如溴乙烷与钠反应为：2CH3CH2Br+2Na→CH3CH2CH2CH3+2NaBr，应用这一反应，下列所给化合物中可以与钠合成环丁烷的是A. CH3CH2Br B. CH3CH2CH2CH2BrC. CH2Br CH2CH2Br D. CH2Br CH2CH2CH2Br