问题 选择题

下列有关化学用语表述正确的是

A.羟甲基(-CH2OH)和甲氧基(CH3O-)电子数不相等

B.S2的结构示意图:

C.质子数为53,中子数为78的碘原子:

D.苯甲醛:

答案

答案:C

题目分析:A、两种基团原子数目和种类相同,电子数相同,错误;B、硫离子得到电子最外层电子数为8个,错误;C、正确;D、醛基书写错误,错误。

单项选择题

A punctual person is in the habit of doing a thing at the proper time and is never late in keeping an appointment.

The unpunctual man, on one hand, never does what he has to do at the proper time. He is always in a hurry and in the end loses both time and his good name. A lost thing may be found again, but lost time can never be regained. Time is more valuable than material things. In fact, time is life itself. The unpunctual man is for ever wasting and mismanaging his most valuable asset as well as other’s. The unpunctual person is always complaining that he finds no time to answer letters, or return calls or keep appointments promptly. But the man who really has a great deal to do is very careful of his time and seldom complains of want of it. He knows that he can not get through his huge amount of work unless he faithfully keeps every piece of work when it has to be attended to.

Failure to be punctual in keeping one’s appointments is the sign of disrespect towards others. If a person is invited to dinner and arrives later than the appointed time, he keeps all the other guests waiting for him. Usually this will be regarded as a great disrespect to the host and all other guests present.

Unpunctuality, moreover, is very harmful when it comes to do one’s duty, whether public or private. Imagine how it would be if those who are put in charge of important tasks failed to be at their proper place at the appointed time. A man who is known to be habitually unpunctual is never trusted by his friends or fellow men.

According to the third paragraph, when you are invited to dinner, you should arrive there ().

A. after other guests have arrived

B. before all other guests

C. at the appointed time

D. after the host has got things ready

问答题 简答题