溃疡疮口太小，脓腐难去，常用的腐蚀药是（） A.红灵丹 B.白降丹 C.七三丹 D.

The purpose of (66) is to enlarge the (67) , the set of addresses a program can utilize. For example, it might contain twice as many addresses as main memory. A program using all of it, therefore, would not be able to fit in main memory all at once. Nevertheless, the computer could execute such a program by Copying into main memory those portions of the program needed at any given point during execution.
To facilitate copying (66) into real memory, the operating system divides it into pages, each of which contains a fixed number of addresses. Each page is stored on a disk until ii is needed. When the page is needed, the operating system copies it from disk to main memory, translating the (68) into real addresses. The process of translating virtual addresses into real addresses is called (69) . The copying of virtual pages from disk to main memory is known as (70) or swapping.

A．paging

B．paragraphing

C．storing

D．changing

环境卫生学主要研究（）

A.自然环境与人群健康的关系

B.生活环境与人群健康的关系

C.生产和生活环境与人群健康的关系

D.生活居住环境和自然环境与人群健康的关系

E.职业与生活环境与人群健康的关系

运用毫米刻度尺和天平（附砝码），设计测量密度为ρ的长方形金箔厚度的方法（金箔的面积较大，质量也较大，但未超过天平的称量，厚度远小于1mm）．

（1）写出实验的主要步骤和需要测量的物理量（用相应的字母表示）．

（2）写出待测金箔厚度的表达式．

______可以按照某种属性或类别的顺序重组，各组观察单位数有等级顺序。

A．等级资料
B．数值资料
C．定量资料
D．分类资料

使用卫星开展远程教育的主要缺点是实时性差、交互性差。