(D)
Plastic is one of the most-used materials for making many things. Things made of plastic can be very strong and last a long time. Plastic is also much lighter than metal and can easily be formed into different shapes. But the wide use of plastics across the world is causing big problems for the environment. Plastics can take hundreds of years to break down on their own.
And very few kinds are highly recyclable.
But a team of researchers working at the U. S. Department of Energy says it has created a kind of plastic that could lead to products that are 100 percent recyclable. I recently reported the discovery in a study in the journal Nature Chemistry.
The researchers say the new material is a plastic polymer（聚合体）named polydiketoenamine, or PDK. The team reports that the material can be broken down in parts at the molecular（分子的）level. It can then be built up again to form plastics of different shapes, textures, colors and more. The researchers say this process can be repeated over and over again.
"Most plastics were never made to be recycled," lead researcher Peter Christensen said in a statement. "But we have discovered a new way to recycle plastics at a molecular level"
The team explained that all plastics are made up of monomers（单体）. Many plastics have different chemicals（化学品）added to them to make them more useful and powerful. The problem is that these chemicals will remain in the monomers even after the material gets processed at a recycling factory. The research team reported that, with the newly discovered PDK material, the monomers could be separated from any chemicals and recycled.
Next, the researchers plan to develop PDK plastics "with a wide range of thermal and mechanical properties. "These plastics could be used for many kinds of cloth, as well as things such as 3D printed materials and foams. What's more, the team is looking to include plant-based materials in the process.
27. What is the first paragraph mainly about?
A. Plastic is a good material.
B. Plastic is widely used in our life.
C. Plastic causes many environmental problems.
D. Plastic has both advantages and disadvantages.
28. The underlined word "It" in Paragraph 3 refers to _______________.
A. the new material B. the research team
C. the monocular level D. the producing process
29. Why do many plastics have different chemicals added to them?
A. To make them easy to break down.
B. To make them stronger and more widely used.
C. To make them easy to get processed in a factory.
D. To make it possible for them to be highly recycled.
30. According to the passage, the writer thinks the future of PDK is to be ____________.
A. worrying B. moving C. hopeful D. awful
DABC
Plastic is one of the most-used materials for making many things. Things made of plastic can be very strong and last a long time. Plastic is also much lighter than metal and can easily be formed into different shapes. But the wide use of plastics across the world is causing big problems for the environment. Plastics can take hundreds of years to break down on their own.
And very few kinds are highly recyclable.
But a team of researchers working at the U. S. Department of Energy says it has created a kind of plastic that could lead to products that are 100 percent recyclable. I recently reported the discovery in a study in the journal Nature Chemistry.
The researchers say the new material is a plastic polymer（聚合体）named polydiketoenamine, or PDK. The team reports that the material can be broken down in parts at the molecular（分子的）level. It can then be built up again to form plastics of different shapes, textures, colors and more. The researchers say this process can be repeated over and over again.
"Most plastics were never made to be recycled," lead researcher Peter Christensen said in a statement. "But we have discovered a new way to recycle plastics at a molecular level"
The team explained that all plastics are made up of monomers（单体）. Many plastics have different chemicals（化学品）added to them to make them more useful and powerful. The problem is that these chemicals will remain in the monomers even after the material gets processed at a recycling factory. The research team reported that, with the newly discovered PDK material, the monomers could be separated from any chemicals and recycled.
Next, the researchers plan to develop PDK plastics "with a wide range of thermal and mechanical properties. "These plastics could be used for many kinds of cloth, as well as things such as 3D printed materials and foams. What's more, the team is looking to include plant-based materials in the process.
27. What is the first paragraph mainly about?
A. Plastic is a good material.
B. Plastic is widely used in our life.
C. Plastic causes many environmental problems.
D. Plastic has both advantages and disadvantages.
28. The underlined word "It" in Paragraph 3 refers to _______________.
A. the new material B. the research team
C. the monocular level D. the producing process
29. Why do many plastics have different chemicals added to them?
A. To make them easy to break down.
B. To make them stronger and more widely used.
C. To make them easy to get processed in a factory.
D. To make it possible for them to be highly recycled.
30. According to the passage, the writer thinks the future of PDK is to be ____________.
A. worrying B. moving C. hopeful D. awful
DABC
