2019年全国统一考试（天津卷）英语独家解析(24)

B. Rapid economic development threatens animal habitats.
C. Species of commercial value dominate other species.
D. Industrial activities help keep food webs stable.
50. How does an early-warning system help us maintain the ecological balance?
A. By getting illegal practices under control
B. By stopping us from killing large predators.
C. By bringing the broken-down ecosystems back to normal.
D. By signaling the urgent need for taking preventive action.
【答案】46. B 47. C 48. D 49. A 50. D
【刘凯解析】
这是一篇说明文。本文介绍了借助食物网的数学模型，科学家们发现了一些食物网运行的关键原则。科学家们说一个生态系统越过了它的临界点，它们很难再回来。科学家们已经建立了一个基于数学模型的预警系统，该系统将会发出信号告诉我们人类活动正将生态系统推向崩溃，允许我们采取措施将生态系统从边缘拉回来。
【46题详解】
细节理解题。根据第一段中With such models, scientists have found out some key principles operating in food webs.可知，借助食物网的数学模型，科学家们发现了食物网中的一些关键原则。故选B。
【47题详解】
细节理解题。根据第二段中When a predator(掠食动物) always eats huge numbers of a single prey(猎物), the two species are strongly linked; when a predator lives on various species, they are weakly linked.可知，当捕食者总是吃大量的单一猎物，这两个物种是紧密相连的。故选C。