You are presented with the question "what causes a solid to form?" and the following answer choices: 
- sunlight
 - evaporative cooling
 - gases
 - Physical weathering
 - water evaporation
 - lower temperature thresholds
 - exposure to cold
 - fissures of hot, acidic water

Now knowing that freezing causes a solid to form and lower temperature thresholds are at freezing, choose the best answer.


 

      lower temperature thresholds   