根据火场残留物被烧的轻重程度，一般将（）初步确定为起火点。A、局部出现灰化区或炭化区

短文改错

Yesterday a school boy is daydreaming in class.Not knowing that he was doing, he put a pen cap

into his mouth.A few minutes late, he was terrified to find that he had swallowed it!The teacher was

shocking when the boy stood up and said, "I've just swallowed a pen cap."He was quickly sent the

nearest hospital.There a doctor examined his and said the best treatment was to take some medicines

so that the pen cap could pass natural.Three hours later the boy successfully made it."She is really lucky, " said the doctor."It's not rare that small children put things into their mouths for a fun.It's very danger."

___________________________________________________________________________

—        ?

—Nothing serious, but a bit tired.                

A．Is that all

B．Is there anything else?

C．What’s this

D．What’s the matter with you

W、X、Z是原子序数依次增大的同一短周期元素，W、X是金属元素，Y、Z是非金属元素。

（1）W、X各自的最高价氧化物对应的水化物可以反应生成盐和水，该反应的离子方程式为

______________________。

（2）W与Y可形成化合物W₂Y，该化合物的电子式为____________________。

（3）X的硝酸盐水溶液显_________性，用离子方程式解释原因：___________________。

（4）Y的低价氧化物通入Z单质的水溶液中，发生反应的化学方程式为_______________

（5）比较Y、Z气态氢化物的稳定性：_____________＞____________（用分子式表示）。

（6）W、X、Y、Z因种元素简单离子的离子半径由大到小的顺序是 ________＞ _______＞ _______ ＞ ________。

（7）Z的最高价氧化物为无色液体，0.25 mol 该物质与一定量水混合得到一种稀溶液，并放出Q kJ 的热量。写出该反应的热化学方程式： ______________________________。

皮带运输机为什么设置张紧装置？

车钩钩舌推铁的作用是推动钩舌张开达到（）位置。

A.开锁

B.闭锁

C.全开