What is a good way to save paper?

Correct answer: Writing on both sides

The governing concept is resource conservation, especially the Reduce principle in the 3R approach: Reduce, Reuse and Recycle. Writing on both sides of a sheet allows more information to be recorded with fewer sheets. As a result, paper consumption is reduced, and fewer raw materials, water and energy may be needed for paper production. Option D is therefore correct. Option A wastes usable paper, while option B deliberately leaves part of each sheet unused. Option C destroys books, creates smoke and does not conserve paper. In practice, paper should be used carefully, blank portions can sometimes be reused for rough work, and unwanted paper should be recycled after use.