What is the name of the effect, named after a 19th Century Austrian physicist, which causes the sound of a moving object to change its pitch as it approaches and then passes you?

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?

Is a light-year a measure of speed, time, or distance?

How many square millimeters are there in a square hectometer?

The first microwave ovens were created in which decade: 1970's, 1960's, 1950's, or 1940's?