再生障碍性贫血最易与下列哪种疾病混淆（）

A.白细胞减少性白血病

B.特发性血小板减少性紫癜

C.阵发性睡眠性血红蛋白尿

D.脾功能亢进

E.骨髓纤维化症

The main feature of (72) is that they follow a first-come/first-served rule. For instance, the line of (73) waiting to be run on a computer system.

A．looplinks

B．queues

C．stacks

D．trees