What kind of thin, wispy, feathery looking clouds, located four to twelve miles up, are usually the first sign that a weather front is approaching?

What gas do plants absorb from the atmosphere during photosynthesis?

What is the chemical symbol for gold?

What element does the symbol Fe represent?

This organ in the human body, about the size of your fist, is located behind the stomach. Its most important function is filtering foreign substances from the blood, as well as helping the body fight infections. What is the name of this organ?

In its basic form, this substance is a kind of soap, but when mixed with gasoline, it forms a deadly material used in flame throwers and incendiary bombs. What is it?

What does a paleontologist study?