车辆所使用的汽油牌号主要取决于发动机的压缩比。

阅读下面的材料，回答问题：

解方程x⁴-5x²+4=0，这是一个一元四次方程，根据该方程的特点，它的解法通常是：

设x²=y，那么x⁴=y²，于是原方程可变为y²-5y+4=0  ①，解得y₁=1，y₂=4．

当y=1时，x²=1，∴x=±1；

当y=4时，x²=4，∴x=±2；

∴原方程有四个根：x₁=1，x₂=-1，x₃=2，x₄=-2．

（1）在由原方程得到方程①的过程中，利用______法达到______的目的，体现了数学的转化思想．

（2）解方程（x²+x）²-4（x²+x）-12=0．

船舶电台必须核配（）.

A.设备说明书

B.电路图

C.电台执照

D.天线布置图

Extract 1

A stylish dining room with cream walls and curtains and black carpet as perfect foil to an eclectic array of furniture. Many of the pieces are classics of their particular era, and demonstrate how old and new designs can be happily mixed together. The prototype chair in the foreground has yet to prove its staying power and was thought up by the flat’s occupant. He is pictured in his living room which has the same decorative theme and is linked to the dining room by a high Medieval-styled archway where was once a redundant and uninspiring fireplace.

Extract 2

Old bathrooms often contain a great deal of ugly pipework in need of disguising. This can either be done by boxing in the exposed pipes, or by fitting wood paneling over them.

As wood paneling can be secured over almost anything — including old ceramic tiles and chipped walls — is an effective way of disguising pipework as well as being an attractive form of decoration. The paneling can be vertical, horizontal or diagonal.

An alternative way to approach the problem of exposed pipes is to actually make them a feature of the room by picking the pipework out in bright p colours.

Extract 3

Cooking takes second place in this charming room which; with its deep armchairs, is more of a sitting room than a kitchen, and the new Rayburn stove as a good Choice, as it blends in well with the old brick and beamed fireplace. There are no fitted units or built-in appliances, so all food preparation is done at the big farmhouse table in the foreground; and the china, pots and pans have been deliberately left on show to make an attractive display, What about the kitchen sink It’s hidden away behind an archway which leads into a small scullery. Here there’s a second cooker and — in the best farmhouse tradition — a huge walk-in larder for all food storage.

Compared with Extract 1 the room described in Extract 3 appears to（）.

A．be more comfortable

B．be more colourful

C．contain more furniture

D．possess a greater variety of style

在额定负载下满是执行机构所要求的速度范围指液压系统的是（）

A.调速范围

B.速度刚度

C.回路效率

D.以上都是

组织机构决策的特点是（）

A.不稳定性

B.战略性

C.非程序性

D.风险性

E.合作性