What do these two changes have in common?
an old sandwich rotting in a trashcan
chicken cooking in an oven

 - Both are chemical changes.
 - Both are only physical changes.
 - Both are caused by cooling.
 - Both are caused by heating.
Step 1: Think about each change.
A sandwich rotting is a chemical change. The matter in the sandwich breaks down and slowly turns into a different type of matter.
Cooking chicken is a chemical change. The heat causes the matter in the chicken to change. Cooked chicken and raw chicken are different types of matter.
Step 2: Look at each answer choice.
Both are only physical changes.
Both changes are chemical changes. They are not physical changes.
Both are chemical changes.
Both changes are chemical changes. The type of matter before and after each change is different.
Both are caused by heating.
Cooking is caused by heating. But a sandwich rotting is not.
Both are caused by cooling.
Neither change is caused by cooling.