Answer: combining rubber with sulphur
Step-by-step explanation:
Chemical change is the change in which chemical composition of the substance changes by rearrangement of atoms.
Physical change is a change in which only the physical properties such as size, shape etc change and there is no rearrangement of atoms.
1. Deflating a rubber balloon only decreases the size of balloon and hence is a physical change.
2. Combining rubber with sulphur is vulcanisation in which sulphur forms bonds with rubber and thus is a chemical change.
3. Stretching an elastic rubber band only changes the shape and hence is a physical change.
4. Erasing pencil marks from a page does not involve any rearrangement of atoms and thus is a physical change.