An example of a grad-school level question?
Swamp plants die, fall to the ground, and are buried by other dying plants. Approximately how long would it take for plants to possibly become a fossil fuel?

An example of a grad-school level question?
Which is the best explanation for how air masses move across the United States?

An example of a grad-school level question?
Which simple machine increases the distance over which a load travels and reduces the needed force?

An example of a grad-school level question?
Which form of water is most likely to appear when the temperature is below freezing?