单位时间内通过单位宽度的人流数量称为（）。

A.人员行进速度

B.流动系数

C.人员密度

D.以上选项均不对

Personal computers are used by one person at a time. The largest personal computer, or PC.S, can fit on a (1) . Some of these (2) have more than one microprocessor. (3) the primary processor, which is a general-purpose device, a PC may have one or more processors to (4) special kinds of work. Some machines, (5) , have maths processors, others have graphics processors to help process photographs and other illustrations. Still others have (6) processors.

Office workers also use PCS that are not (7) to a network. These machines are used for (8) tasks as word processing, performing financial calculations, and organizing and (9) bodies of information called databases. People use PCS at (10) for some of the same kinds of tasks. They use word processing programs for (11) communication, financial software for household budgets. Individuals also use their home computers to play (12) and to communicate (13) the internet.

Small, portable PCS are (14) with people who often work away from their desks. The (15) include laptop computers, which can be (16) on the lap; notebook computers, which are about the (17) of a loose leaf notebook; and palmtop, or handheld computers, which can be operated while (18) in the hand. Laptop and notebook computers have the same (19) as desktop computers. Palmtop computers have less power but still (20) some advanced capabilities. For example, they can process household financial data.

9（）

A.sorting 

B.dividing 

C.to arrange 

D.to separate