题目

阅读理解 Hummingbirds(蜂鸟) are one of nature's most energetic fliers and the only birds to hover(盘旋) in the air by relying on their strength alone. Now scientists have found that it is the ratio(比值) of the bird's wing length to its width that makes them so efficient. The discovery is helping experts compete with 42 million years of natural selection to build helicopters that are increasingly efficient. David Lentink, an assistant professor at Stanford University in California, tested wings from 12 different species of hummingbirds, which he sourced from museums. He placed them o有学者认为，明清之际的中国思想界，“以复古开新的模式完成了集古代思想之大成。”所谓“复古开新”，主要体现在 ①先秦民本观念复兴             ②工商皆本思想提出 ③君主专制受到批判             ④经世致用思潮形成 A．①②③ B．①②④ C．②③④ D．①②③④