2. Cut the cardboard into circles with the same size, as shown in the figure.
3. Drill a hole the size of a pencil rod in the middle of the disc.
4. Keep a complete disc, and cut the other two, with moderate size.
5. Fix with double-sided adhesive tape.
6. Put a pencil stick or something on the CD.
A. Which is better, mushrooms or learning and thinking?
The principle of integrating theory with practice is determined by the applied scientific natur