When blood is first pumped out of the human heart, it first enters a certain organ, then it returns to the heart a second time before continuing its trip through the body. Which organ is this?

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?