Question: The metal lid on a glass jar is hard to open, so it is held under warm, running water. What causes the jar to open easily after it was held under the water?

  Options: 
 A. The water increased the pressure under the lid.
 B. The jar shrunk with the warm water.
 C. The water acted as a lubricant between the glass and the metal.
 D. The metal lid expanded under warm water.
Answer: D