A．He has climbed mountains using a stick.B．He has climbed mountains riding a horse.C．He has climbed mountains supported by a guider.D．He has climbed mountains using a system he devised himself.
A．He has climbed mountains using a stick.
B．He has climbed mountains riding a horse.
C．He has climbed mountains supported by a guider.
D．He has climbed mountains using a system he devised himself.