You are presented with the question "Why does water sink in oil?" and the following answer choices: 
- gravity
 - flooding
 - salinity
 - sun's heat
 - explosion
 - water vapor
 - combustion
 - erosion

Now knowing that if an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity and oil is less dense than water, choose the best answer.


 

 gravity        