Question: A dish of sugar water was left on a window sill. One week later, there were only sugar crystals left in the dish. The water was gone. The best explanation for the appearance of sugar crystals is

  Options: 
 A. some of the water was absorbed by the dish.
 B. the air condensed.
 C. the light shining on the window sill produced more sugar.
 D. the water evaporated.
Answer: D