You are presented with the question "Contact between solid mineral deposits over long periods of what causes them to smooth" and the following answer choices: 
- time
 - vacuum
 - widen
 - cracks
 - clocks
 - years
 - Bend
 - instant

Now knowing that contact between rocks over long periods of time causes rocks to smooth and rocks are actually solid mineral deposits, choose the best answer.


 

 time        