Jack’s brother bought a magazine called Choice. It introduces to its readers information about all kinds of products like cameras, computers, cars, etc. This information helps them make the best choice when they buy something.

Jack borrowed his brother’s magazine when he needed a new computer. “I’ll read about all the different computers,” he said, “And I’ll choose the best one.”

ThinkPad G450M-T4300: This computer comes with lots of good software. However it does not have much memory and is rather slow. At $3,600, it’s not very good value for money.

HP CQ40-506AX: This is the most expensive computer we tasted. However it is also the most

reliable(值得信赖的). It is very fast and has lots of memory. Though it’s 600 dollars more expensive than ThinkPad G450M-T4300, it is worth the extra money if you can afford it.

The Acer A175-78: At only $2,600, this is the cheapest computer we tasted. It has plenty of memory and is quite fast. However, it “crashed” twice while we were testing it and we cannot recommend(推荐) it for reliability.

Jack choose HP CQ40-506AX. “I know it’s expensive, brother,” he said. “But it will last me a long time and do everything I want it to do.”

[化学-物质结构与性质]

W、X、Y、Z 4种元素原子序数依次减小．W的原子序数为24；X原子p轨道共有11个电子；Y是第三周期主族元素，其部分电离能（I）如下表；Z原子价电子排布式为nsⁿnpⁿ．请回答下列问题：

（2）电负性：X______Y（填“＞”、“=”或“＜”）．

（3）R是与X同主族的短周期元素．R的氢化物沸点比X的氢化物更高，原因是：______．

（4）氨为常见化工原料，氨分子中N原子采用______杂化，该分子的空间构型为______，分子中N、H原子之间形成______（填“σ”或“π”）键；

已知W³⁺能与氨分子形成配离子[W（NH₃）₆]³⁺，该配离子中存在的化学键有______．（填标号）

A．金属键    B．离子键    C．共价键    D．配位键．