试题与答案

下列说法中正确的是( ) A.难失电子的原子,获得电子的能力一定强 B.易得

题型:选择题

题目:

下列说法中正确的是(  )

A.难失电子的原子,获得电子的能力一定强

B.易得电子的原子所形成的简单阴离子,其还原性一定强

C.分子中键能越大,键长越长,则分子越稳定

D.电子层结构相同的不同离子,核电荷数越多半径越小

答案:

D

A错误,ⅣA的元素最外层有4个电子,既难失电子,也难获得电子;B错误,易得电子的原子所形成的简单阴离子,其还原性弱;C错误,分子中键能越大,键长越短,分子越稳定;D正确,电子层结构相同的不同离子,核电荷数越多,原子对电子的吸引力越强,半径越小。

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题型:单项选择题

(21) put computers to practical business use, but below the surface it is the heart of an (22) - the kernel - that provides the technical wizardry to juggle multiple programs, connect to networks and store (23) .
A traditional kernel provides all the functions for applications. The kernel (24) memory, I/O devices and parcels out processor time.
The kernel also supports (25) and fault tolerance, which is the ability to recover automatically when parts of the system fail.

A.Databases

B.Applications

C.Drivers

D.Games

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