Paper was improved by a Chinese man called Cai Lun in 105 AD. In the 1lth century, China began to use paper money. 【小题1】. At that time, people made paper from the wood of a special kind of tree.

【小题2】. And more and more paper is used. You know, 17 trees are needed to make one ton of paper. And it takes more than 10 years for a tree to grow. It is clear that there will be fewer and fewer trees left on Earth soon. Therefore, 【小题3】.

Now we know it is important not to waste paper. 【小题4】 First, we can use both sides of every piece of paper. Second, we can put drinks in bottles instead of paper boxes. 【小题5】. We can also use handkerchiefs instead of tissues. Last, we can reuse envelopes (信封). We can use fewer paper shopping bags by reusing them as well.