Of course you always have to balance yourself when you are on a bike. That's easy when you are pedaling but harder when you are stopped. When you are pedaling, the wheels are spinning. That makes your bike a gyroscope. A wheel spinning in an upright position tends to keep that position. That same idea also works for other things. You may have noticed that a spinning top falls over when it stops spinning. Which best describes the main idea of the passage?
A.
the reason people enjoy riding bicycles
B.
why tops fall over when they stop spinning
C.
why some children fall off their bicycles
D.
the science behind balancing on a bicycle