Fact 1: If an object in a fluid is more dense than that fluid then that object will sink in that fluid because of gravity.

Fact 2: Oil is less dense than water.

Given the two facts above, answer the question "Why does water sink in oil?" with the following options: 
- gravity
 - flooding
 - salinity
 - sun's heat
 - explosion
 - water vapor
 - combustion
 - erosion


 

 gravity        