What do these two changes have in common?
a crayon melting in the sun
mixing sand and water

 - Both are chemical changes.
 - Both are caused by heating.
 - Both are only physical changes.
 - Both are caused by cooling.
Step 1: Think about each change.
A crayon melting in the sun is a change of state. So, it is a physical change. The crayon changes state from solid to liquid. The crayon is still made of wax, even after it melts.
Mixing sand and water is a physical change. Adding water makes the sand wet. But both the sand and water are still made of the same type of matter as before.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are physical changes. No new matter is created.
Both are chemical changes.
Both changes are physical changes. They are not chemical changes.
Both are caused by heating.
A crayon melting in the sun is caused by heating. But mixing sand and water is not.
Both are caused by cooling.
Neither change is caused by cooling.