What do these two changes have in common?
water evaporating from a lake
mixing sand and gravel

 - Both are caused by cooling.
 - Both are chemical changes.
 - Both are caused by heating.
 - Both are only physical changes.
Step 1: Think about each change.
Water evaporating from a lake is a change of state. So, it is a physical change. The liquid changes into a gas, but a different type of matter is not formed.
Mixing sand and gravel is a physical change. Together, the sand and gravel make a mixture. But making this mixture 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.
Water evaporating is caused by heating. But mixing sand and gravel is not.
Both are caused by cooling.
Neither change is caused by cooling.