Which change is the best example of a physical change 1) a cookie baking 2) paper burning 3) ice cream melting 4) a nail rusting

Hey there! :D

We want to find an answer choice that is reversible. If the physical change could have some way of being fixed, then it is a physical change. If it is a chemical change, the make-up is different and there is no way that it could change. 

A cookie baking cannot be reversed. Cookies cannot go back to being cookie dough. 

Paper burning cannot be reversed. Ashes and smoke cannot go back to being paper. 

However, if your ice cream melts, you can refreeze it. Therefore, "3" is the best answer to the question. 

I hope this helps!
~kaikers