44. B 细节理解题。根据第一段第二句"Sadly, biological facts prevent us ever accomplishing such a thing without artificial aid - we simply weigh too much, and all our mass pushes down through our relatively small feet, resulting in a lot of pressure that makes us sink."可知，由于人类有生物方面的限制，在水上行走不会成为现实。故选B项。

45. C 细节理解题。根据第二段第三句"It can run across water for a distance of several meters, avoiding getting wet by rapidly hitting the water's surface with its feet."可知，蜥蜴能通过快速拍击水面穿越水面。故选C项。

46. A 细节理解题。根据第三段第二句可知，cornflour的功能是可以创建一种和水的厚度不一样的液体。故选A项。

47. D 观点态度题。根据第四段第一句"Fun though all this may sound, it's still rather messy and better read about in theory than carried out in practice."可推断，作者认为人在水上行走的想法在理论上可行，但不实际。故选D项。