Here's a problem to solve: Students want to raise the temperature of water in a glass jar. The jar is on a table in full sunlight. The fastest way to increase the temperature without using a hot plate is to place

Among the 4 following options, which is the correct answer?

- A: a straw in the water.
 
- B: clear plastic wrap around the glass.
 
- C: a thermometer in the water.
 
- D: black material around the glass.
 