An example of a grad-school level question?
What causes the blue color of the sky?

An example of a grad-school level question?
In Alaska, there are fewer hours of daylight in the winter than in the summer. Which statement best explains why this difference occurs?

An example of a grad-school level question?
In most animals, combinations of various tissues make up functional units called

An example of a grad-school level question?
The principle of uniformitarianism states that most of the landscape of Earth was formed slowly and over a long period of time. Which occurrence of Earth is least supported by this principle?