Generate two ways to classify the following objects: paper, pencil, eraser, ruler.
1) Writing Instruments and Accessories:
- Writing Instruments: Pencil
- Accessories: Paper, Eraser, Ruler

2) Stationery Items by Physical Properties:
- Flexible: Paper
- Rigid: Pencil, Eraser, Ruler.
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate two ways to classify the following objects: paper, pencil, eraser, ruler.

### Output:
1) Writing Instruments and Accessories:
- Writing Instruments: Pencil
- Accessories: Paper, Eraser, Ruler

2) Stationery Items by Physical Properties:
- Flexible: Paper
- Rigid: Pencil, Eraser, Ruler.