What do we call an organism that lives on a host which it usually injures?

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?

What does a paleontologist study?

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?

Which New Testament woman can be considered either a woman whom Jesus cured of evil spirits, or a repentent prostitute who washed the feet of Jesus?

In terms of personal computer use, the United States leads the world with almost 150 million personal computers in use. Which three countries follow in total computers?

How many square millimeters are there in a square hectometer?