People should recycle more plastic stuff.
More plastic stuff should be recycled by people.
Engineers should build more energy-efficient fridges.
More energy-efficient fridges should be built by engineers.
Designers can use natural and renewable materials to make clothes.
Natural and renewable materials can be used by designers ...
People can melt and reuse glass again to make windows.
Glass can be melted and reused by people .....
People should use natural materials more often.
Natural materials should be used ...
We can grow renewable materials like cotton on farms.
Renewable materials like cotton can be grown ...
We can recycle some man-made materials like plastic.
Some man-made materials like plastic can be recycled.
People must design more energy-efficient cars.
More energy-efficient cars must be designed.
We should close the windows to conserve energy.
The windows should be closed ...
