肝豆状核变性是由下列哪项引起的（）

A.铁代谢障碍

B.铜代谢障碍

C.锌代谢障碍

D.铝代谢障碍

E.钙代谢障碍

Chain suspension ladders on a ship must be replaced by fixed ladders if the required chain suspension ladder（）.

A.has been sent in for repair

B.cannot be supported against a vertical flat surface

C.does not extend to the water when the ship lists 15 degrees

D.is not equipped with vertical guard rails on either side