申論題

   Six hundredmillion hungry rabbits can be harmful. They ate native plantspecies __61__ they disappeared. They competed forfood and shelter __62__ native animals.And they were a nightmare for cattle and sheep farmers, __63__ animals couldn’t get enough grassto eat and starved. The rabbits did some good, of course. They provided food __64__ poorfamilies. They helped fur and __65__ industries. But theirimpact on the environment andmajorlivestock economy was __66__ negative to be ignored. People tried trapping them. They even built a huge wall againstthem.Aftermuch testing,the deadlymyxoma virus was unleashed on Australia’srabbits. Itwas a huge success. Cattle and sheep ranching bounced back, and threatened plants were better protected.However,rabbits became __67__ to the virus.Another viruswas introduced, and it had good results. The rabbits are under controlfor now, and the continent haslearned to be __68__with newspecies.