1 .
Directions:Complete the following sentences by using the proper form of the words or expressions
given in the frame.Each one can only be used once.
A. capable B. effectiveness C. employing D.exposure E.famously
F. joining G. limitation H. minimal I.precisely J.recognizing K.worthwhile |
Clean Air Act
The air in modern homes and offices is pretty clean,but not as clean as it might be.Often it contains small amounts of volatile(挥发性的）,poisonous,organic compounds.Long-term 1 to these is a bad thing,so clearing them out of the air people breathe is widely accepted as 2
Finding an effective way to do so has proved difficult.But Stuart Strand, Long Zhang and Ryan Routsong, of the University of Washington,in Seattle,think they have succeeded,As they report in Environmental Science and Technology, their method involves 3 a gene from a rabbit into a popular indoor plant nicknamed Devil's vine—a type of ivy hat is so called because it is 4 difficult to kill.
The idea of 5 plants to de- pollute the atmosphere inside buildings has been around for decades-but has met with only qualified success. One experiment involving unmodified spider plants,for example,showed that they are indeed 6 of removing formaldhyde (甲醛) from the air.The 7 is that to make much of a difference in a space as large as a house would require turning most of the rooms into spider-plant forests.
Dr Strand, Dr Zhang and Mr Routsong thus sought something suitably transgenic ( 转 基 因 的),but that does not flower indoors. The plant they settled on was Devil's vine, 8 because of its toughness.With the help of a bacterium,they were able to ferry the rabbit version of the gene into the plant's chromosomes(染色 体),and thus to,engineer a type of Devil's vine able to produce an air-cleaning substance. To test the 9 of their idea, the researchers put their modified ivy to work inside greenhouses filled with air containing high levels of harmful substances.The plants performed well,reducing the harmful substances in air to 10 .
