Physical change means there is no new substance created or can be observed. The substance still retain their own properties and its still the same kind of substance.
The answer is D, freezing water. When you freeze water, you only changes its state of matter. Ice is still water, and you can return it back to liquid by melting it (apply heat).
Comparing to all the other choices, A, burning wood, you apply heat and fire to wood and it gives out substances such as smoke, carbon dioxide etc. Their is new substance formed.
And B, rusting metal, rust is a kind of new substance that doesn't originally belongs to the metal. Rust forms when the metal chemically reacts to substances such as oxygen.
And C, you have changed the protein sequence of the egg, it can no longer form back into its original raw state. The texture and color may have changed.
Therefore, your answer is D.
