Read the passage below carefully, and then choose the best answer

Background, in relation to computers, on the screen, the color on which characters are displayed. (1) _______, a white background may be used for black characters. In a windowing environment in which more than one program or document can be available to the user, open but currently inactive (2) _______ are said to be in the background.

In the context of operating systems and program execution, background refers to a process, or task, assigned a lower priority in the microprocessor's share of time to tasks other than the task running in the (3) _______. A background process thus often performs its work, such as printing or checking for arriving messages on an electronic mail network, invisibly unless the user requests an update or brings the task to the foreground. (4) _______, only multitasking operating systems are able to support background processing. However, some operating systems that do not support multitasking may be able to perform one or more types of background tasks. For example, in the Apple Macintosh operating system running in Single-Launch Mode (with multitasking (5) _______), the Background Printing option can be used to print documents while the user is doing other work.

(1) ....................

• A. 
  For sure
• B. 
  In fact
• C. 
  For example
• D. 
  In general