Read the passage carefully and choose the correct answer.
By the year 2025, the Earth could lose as many as one fifth of all species known to exist today. In recent centuries, hundreds of species have disappeared, almost always as a result of human activities. The passenger pigeon, one familiar example, was a source of food until excessive hunting and habitat loss caused its extinction in 1914. The North American bison, whose populations were decimated by settlers and market hunters in the 1800s, came close to sharing the same fate. Bison survive today only because of the efforts of early conservationists.
Today, species require such efforts more urgently than ever. An essential task that falls to present-day conservationists is to determine which species are most, endangered, so that conservation resources' can be applied where action is needed most. Species are categorized by the degree to which their survival in the wild is threatene World Wildlife Fund offers a sampling of animals and plants that fall mainly within the two most serious categories of- threat: critically endangered and endangere What threatens these species' existence? Some of the top threats are habitat destruction by unsustainable logging and ever-encroaching human settlement; pollution of water, soil, and air by toxic chemicals; unnatural climate changes due to fossil fuel use; unmanaged fishing that exhausts fish stocks; and illegal hunting to supply the demand for skins, hides, traditional medicines, food, and tourist souvenirs. The list which conservationists presents only a fraction of the species at risk of extinction today and does not include thousands of species whose status we do not yet know. Hundreds of species without common names have been left out, which means that while many mammals are on this list, only a few insects and mollusks are include
Species listed here range from the largest animal on Earth, the blue whale, to the majestic tiger, to the humble thick-shell pond snail. Large or small, beautiful or ugly, all species play a role in the complex circle of life. All of us depend on the natural resources of our planet. Each time a species is lost, the complexity, natural balance, and beauty of our world is diminishe And what threatens plants and animals ultimately threatens people as well.
According to the last paragraph, _______.
species extinction has no relationship to human beings what threaten plants and animals can do nothing to human beings human beings depend on natural resources to survive not every, species has a role in the circle of life.