Answer: d. cracking an egg
Step-by-step explanation:
A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.
A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.
1. Boiling soup : Only the phase change takes place, thus a physical change and can be reversed by condensation.
2. Burning wood: the chemical reaction occurs by combination of wood with oxygen , thus a chemical change.
3. Freezing water: Only the phase change takes place, thus a physical change and can be reversed by melting
4. Cracking an egg: Only the state changes and thus a physical change and cannot be reversed.