We should ( turn off / turn on ) the lights when we don't use.
turn-off
You shouldn't ( save / waste ) water if you want to protect the environment.
waste
We should ( use / reduce ) public transportation.
use
We ( should / shouldn't ) use solar energy.
should
You should ( unplug / plug ) the TV when you don't watch.
unplug
We should use paper bags to ( protect / harm ) the environment.
protect
We should ( cut down / plant ) trees because they produce O2.
plant
You should ( recycle / waste) glass, metal or paper.
recycle
You ( should / shouldn't ) use eco-friendly bulbs to save electricity.
should
We ( should /shouldn't ) use filters because it reduces air pollution.
should
