1. It's our duty to protect our environment.
2. It is very important to take care of our environment.
3. We should not throw litter onto the ground.
4. We should not spit in a public place/cut down the trees.
5. We should plant more flowers and trees.
6. We must pick up some rubbish and throw it into a dustbin.
7. If everyone makes contribution to protecting the environment, the world will become much more beautiful.