A．To help people survive．
B．To give people confidence．
C．To give people the information about the outside world．
D．To make up most of the information about the outside world．

A．In the inner ear．
B．In the external ear．
C．In the brain．
D．In the nerve endings．

A．It is made up of the nerves near muscles．
B．The nerve message knows how to control human's motion．
C．It is produced by our muscles．
D．It is helpful to coordinate the limbs and motion．