单项选择题
A．they were too soft to bear the climber’s weight B．they were the only pitons he could afford to buy C．they coul not last long D．they were made of iron
A．used B．using C．to use D．use
A．not comparable to that of Adams or Madison B．greater than that of either Adams or Madison C．of the same importance as that of Adams and Madison D．second in importance only to that of Adams and Madison