Students should do everything they can __their study.

A．improve

B．to improve

C．improving

D．improved

代谢障碍引起肝硬化的肝豆状核变性(Wi1son病)下列哪项为非特征性的()

A．Kayser-F1eischer角膜色素环

B．血清铜增高

C．血浆铜盐蛋白明显降低

D．尿铜排泄增多

E．肝脏铜含量增多