Do you feel 1     difficult to be happy all the time? Now I’ll give you some tips(秘诀) 2       how to make yourself happy. One way is being   3      (self) because unselfishness is the key factor   4      (require) if you want to get along well with others. By   5    (say) being unselfish we mean we   6     not want everything our own way or demand the best share of everything. Another way is to look for good points in  7      people. You’ll find most people pleasant to get along with and it will surely make you happy. Third, you cannot expect to be too perfect,   8      don’t be too unhappy when you make a mistake. Everything will be OK if you try to make things right. Finally, it is important to remember that while you are not  9      (bad) than others, chances you have may not be much better. In this case,  10      surest way to be happy is to think yourself above other people.

实验室常用饱和NaNO₂与NH₄Cl溶液反应制取纯净的氮气。反应方程式为

NaNO₂+NH₄Cl====NaCl+N₂↑+2H₂O（正反应放热）

如下图所示

（1）装置中，A部分的分液漏斗与蒸馏烧瓶之间连接的导管所起的作用是______________（填写编号）。

a.防止NaNO₂饱和溶液蒸发    b.保证实验装置不漏气    c.使NaNO₂饱和溶液顺利滴下

（2）B部分的作用是_______________________。

a.冷疑                       b.冷却氮气              c.缓冲氮气流

（3）加药品前必须进行的一个操作步骤是____________；加热片刻后即应移去酒精灯以防止反应物冲出，其原因是____________________________。

（4）收集N₂前，必须进行的步骤是（用文字说明）__________________；收集N₂最适宜的方法是（填写编号）______________。

a.用排气法收集在集气瓶中   b.用排水法收集在集气瓶中   c.直接收集在球胆或塑料袋中