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Humans are responsible for causing changes in the environment that hurt animals and species(物种)。We take up more space on Earth for our homes and cities. We pollute habitats(栖息地). 48__________ illegally hunt and kill animals. All of these activities take resources and habitats away 49_______plants and animals.
Hunan activity often changes or destroys the habitats that plants and animals need to survive. 50________ human populations are growing so fast animals and plants are disappearing many times faster51______ they have in the past 65 million years.
Animals and plants have always had a 52______ time surviving. Animals became extinct in the past for a wide variety of reasons. In some cases, competition for resources among animals led to extinction and in 53_______ cases, environmental changes caused extinction.
Fortunately, we humans are beginning to realize our mistakes, 54_____we could destroy everything on Earth. We must not only use our knowledge and abilities to manage the Earth,55________to make the Earth a safe and healthy place where all animals and plants—including humans ourselves –can live.
48.we 49.from 50.because / as / since 51.than
52.hard / difficult 53.other 54.or 55.but