Q: A balloon filled with helium gas is set free and starts to move upward. Which of the following best explains why the helium balloon moves upward?
A: The density of helium is less than the density of air.
Q: Approximately how long does Earth take to complete its orbit around the Sun?
A: one year
Q: A student recorded the amount of rain that fell in one year in his city. What is the best way for him to organize his information?
A: graph
Q: A scientist studies how weathering and erosion can change the shape of a mountain. The scientist needs to collect information over what period of time to gather the most accurate information?
A:
years