（）is a computer technology that headsets,sometimes in combination with physical spaces or multi-projected environments,to generate realisitic images,sounds and other sensations that simulate a user’s physical presence in a virtual or imaginary environment.

“A And B”准则表达式表示的意思是

“A And B”准则表达式表示的意思是______。

For details of these and other lights the larger scale charts and Admiralty Lists should be （）.

Some advanced economies, notably Japan and Germany, fared better than others during the 1970s and 1980s.

When you become frightened, many physical changes occur within your body. Your heartbeat and responses quicken; your pupils dilate(扩大 and _______more light.

Which of the following is true about mental health and physical health?

The use of pulse groups and extremely precise timing at each Loran-C station makes possible the use of（）.

Young children are completely _____ the mother for their physical needs and for their early education and training.

“And now let us begin with lot 1”所表示的中文意思是（）。

There are 11 official languages, including English, Afrikaans and Xhosa, Zulu, Sesotho and other nine African languages.（）

在仪表阀门中，（）一般可以分为EF-1、EF-2、EF-3、EF-4、SS-M2F8等多种类型。