Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[EX Q]: Question: How can you calculate the density of matter? Answer: by dividing its mass by its volume
[EX A]: The density of matter can be calculated by dividing its mass by its volume.

[EX Q]: Question: What plastid makes and stores other pigments? Answer: chromoplasts
[EX A]: Chromoplasts are plastids that make and store other pigments. The red pigment that colors the flower petals in Figure above was made by chromoplasts.

[EX Q]: Question: What harmful substance must not be drained into s storm sewer? Answer: motor oil
[EX A]:
People may dispose of harmful substances incorrectly. For example, motor oil must not be drained into a storm sewer.