it says choose all that apply. meaning there is more than one answer. you only chose one. the answer you chose is correct but "the substance" and "the amount" go along with "difference in temperature". 
 
        
             
        
        
        
The American Dream is out going and most of the time outrageous. Most of the time we dream up those amazing scenario for our future, but we forget about the reality of life. Reality has a way of turning the American Dreams into just a far thought. Reality comes with responsibility and commitment and it is hard to follow your dreams when you realize all the strings that are attached. Reality and dreams don't mix well.
        
             
        
        
        
Answer:
Obstacles
Explanation:
That's most likely what they're looking for.