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【单选题】

Tigers, the largest of the world’s cats, are the heart and soul of Asia’s jungles, grasslands, and deserts. They’re so adaptable that they even thrive in the frigid Himalayan foothills—and they are the dominant predator, literally the kings and queens, of every ecosystem they inhabit. But Asia’s exploding human population is eating away their forest home, and both tigers and their prey have been caught in the crosshairs (瞄准器) , killed in vast numbers by hunters and more recently, by poachers.
In just 100 years’ time, we humans have engineered their grand-scale death. A century ago, more than 100,000 tigers roamed across 30 nations, from Turkey to Siberia, throughout Southeast Asia down to the tip of Indonesia. Today, they hang on in just 12 countries; though they’re the national animal of six nations, they’ve vanished from two of them, North and South Korea. They’ve disappeared from 93 percent of their former range; just 42 breeding populations remain, scattered across the continent. Half of all our wild tigers live in India.
Recently, the Smithsonian Conservation Biology Institute yzed the genetic vigor of tigers in a string of reserves across central India, where I just spent three weeks. One of them, Pench Tiger Reserve, is a 100-square-mile (257-square-kilometer) patch that looks like an illustration from The Jungle Book: groves of towering bamboo, big-leafed teak trees and "strangler fig" banyans filled with acrobatic langur monkeys. But Pench is essentially a leafy island. It’s hard to believe that a century ago, this was mostly unbroken forest. Today it, (like many parks, especially in India) is being squeezed by an encroaching, crowded sea of humanity. These parks are bordered by a patchwork of rice paddies, crop fields, bordering on villages, cities, and all sorts of development. The surrounding land is segmented by roads, railways, scarred by massive mines and other barriers that render it erous and virtually impassable for these wide-ranging predators.
Researchers found that in Pench and other reserves that lacked corridors connecting them to other forests, tigers were far more inbred. Those cats had 47 to 70 percent less gene flow, and as we know from the medical history of European royalty, inbreeding (近亲繁育) does not create the healthiest bloodlines.
Tigers have lived in these lands for thousands of years; like all modern cats, they originated in Southeast Asia. The great roaring cats, Panthera were the first to branch off the cat family tree 10.8 million years ago. It’s a group that includes tigers, lions, leopards, jaguars and snow leopards.
The first paragraph claims all of the following EXCEPT ______.

A.
tigers can survive from harsh environment
B.
Asian tigers dominantly live in forest
C.
Asia’s population growth leads to the decrease of the forest
D.
many tigers are killed by hunters and poachers
题目标签:瞄准
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参考解析:
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举一反三

【单选题】瞄准水准尺的步骤为

A.
目镜对光-初步照准-物镜对光-消除视差;物镜对光-初步照准-目镜对光-消除视差
B.
初步照准-物镜对光-目镜对光-消除视差
C.
消除视差-初步照准-物镜对光-目镜对光

【多选题】瞄准的要领是()。

A.
保持枪身、枪面的平正和一致
B.
保持姿势、重心和力量不变
C.
保持准星和缺口的平正
D.
保持枪支的平稳,自然晃动

【多选题】下列关于瞄准的叙述,正确的有( )。

A.
测角瞄准用的标志一般是标杆、测杆或用三根竹竿悬吊垂球或觇牌
B.
测角瞄准时,首先应转目镜螺旋,使十字丝清晰
C.
瞄准目标一定要注意“先精瞄、后粗瞄的原则”
D.
精瞄准要转动微动螺旋,为提高瞄准的精度转动微动螺旋,最后以旋进结束
E.
瞄准目标时要注意消除视差,眼睛的视线应左右移动观察目标的像与十字丝是否存在错动现象

【单选题】瞄准水准尺时必须()

A.
调清目镜
B.
调平仪器
C.
消除视差
D.
扶好水准尺

【单选题】Genetically-modified foodstuffs are here to stay. That's not to say that food produced by conventional agriculture will disappear, but simply that food-buying patterns will polarize: there will be a n...

A.
Because they will be cheaper than conventional foodstuffs.
B.
Because they will remove people's worries about taking many chemicals.
C.
Because it will be more convenient for people to get them.
D.
Because conventional foodstuffs will not be available in the future.