What do these two changes have in common?
melting wax
dust settling out of the air

 - Both are caused by heating.
 - Both are only physical changes.
 - Both are chemical changes.
 - Both are caused by cooling.
Step 1: Think about each change.
Melting wax is a change of state. So, it is a physical change. The wax changes from solid to liquid. But it is still made of the same type of matter.
Dust settling out of the air is a physical change. As the dust settles, or falls, it might land on furniture or the ground. This separates dust particles from the air, but does not form a different type of matter.
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.
Wax melting is caused by heating. But dust settling out of the air is not.
Both are caused by cooling.
Neither change is caused by cooling.