Dear Jack
I received your letter not long ago. pollution has become a serious problem to us. It means that the air, seas, rivers and land are polluted by waste or poisonous things. It does harm not only to human beings but also to animals （It does harm to animals, as well as human beings.）.low-carbon life is very important for us.. It"s our duty to protect our environment.As a student ,. We should not throw litter onto the ground,. We should not spit in a public place/ cut down the trees. We should plant more flowers and trees.
. If everyone makes contribution to protecting the environment, the world
will become much more beautiful.