下列各项中属于流动资产的有( )。A．机器设备 B．预收账款 C．预提费用 D．预

There are two types of people in the world. Although they have equal degree of health and wealth and other comforts of life, one becomes happy and the other becomes unhappy. This arises from the different ways in which they consider things, persons, events and the resulting effects upon their minds.

People who are to be happy fix their attention on the convenience of things; the pleasant parts of conversation, the well prepared dishes, the goodness of the wine and the fine weather. They enjoy all the cheerful things. Those who are to be unhappy think and speak only of the opposite things. Therefore, they are continually dissatisfied. By their remarks, they sour the pleasure of society, offend(hurt) many people, and make themselves disagreeable everywhere. If this turn of mind was founded in nature, such unhappy persons would be the more to be pitied. The intention of criticizing and being disliked is perhaps taken up by imitation. It grows into a habit, unknown to its possessors. The habit may be p, but it may be cured when those who have it realize its bad effects on their interests and tastes. I hope this little warning may he of service to them, and help them change this habit.

Although in fact it is chiefly an act of the imagination, it has serious results in life since it brings on deep sorrow and bad luck. Those people offend many others; nobody loves them, and no one treats them with more than the most common politeness and respect. This frequently puts them in bad temper and draws them into arguments. If they aim at getting some advantages in social position or fortune, nobody wishes them success. Nor will anyone start a step or speak a word to favor their hopes. If they bring on themselves public objections, no one will defend or excuse them, and many will join to criticize their wrongdoings. These should change this bad habit and be pleased with what is pleasing, without worrying needlessly about themselves and others. If they do not, it will be good for others to avoid any contact with them. Otherwise, it can be disagreeable and sometimes very inconvenient, especially when one becomes mixed up in their quarrels.

We can conclude from the passage that ().

A. we should pity a11 such unhappy people

B. such unhappy people are dangerous to social life

C. people can get rid of the habit of unhappiness

D. unhappy people can not understand happy persons

某化学实验小组同学利用如图1所示装置制备氨气，并探究氨气的性质（部分仪器已略去）．

请回答：

（1）实验室制备氨气的化学方程式为______；干燥氨气常用的干燥剂是______．

（2）收集氨气时，请你选择氨气的进气口______（填“a”或“b”），理由是______．

（3）若观察到装置B中的烧瓶内产生了红色喷泉，则说明氨气具有的性质是______．

（4）为防止环境污染，如图2所示装置（盛放的液体均为水）可用于吸收多余氨气的是______（填序号）．

（5）氨气在催化剂并且加热时会被空气氧化，这是工业制硝酸的第一步反应，写出该反应的化学方程式______．

将电动车的前轮装有发电机，发电机蓄电池连接。当在骑车者用力蹬车或电动自行车自动滑行时，自行车就可以连通发电机向蓄电池充电，将其他形式的能转化成电能储存起来。现有某人骑车以500J的初动能在粗糙的水平路面上滑行，第一次关闭自充电装置，让车自由滑行，其动能随位移变化关系如图线①所示；第二次启动自充电装置，其动能随位移变化关系如图线②所示，则第二次向蓄电池所充的电能是

A．200J

B．250J

C．300J

D．500J

从一副扑克牌（54张）中至少抽出多少张才能保证同一花色的牌有4张呢？

下列电子式正确的是