试述植保机械的维护保养要求。

Acting is such an over-crowded profession that the only advice that should be given to a young person thinking of going on the stage is "Don’’t!". But it is useless to try to discourage someone who feels that he must act, though the chances of his becoming famous are slim. The normal way to begin is to go to a drama school. Usually only students who show promise and talent are accepted, and the course lasts two years. Then the young actor or actress takes up work with a repertory company, usually as an assistant stage manager. This means doing everything that there is to do in the theatre: painting scenery, looking after the furniture, taking care of the costumes, and even acting in very small parts. It is very hard work indeed. The hours are long and the salary is tiny. But young actors with the stage in their blood are happy, waiting for the chances of working with a better company, or perhaps in films or television.Of course, some people have unusual chances which lead to fame and success without this long and dull training. Connie Pratt, for example, was just an ordinary girl working in a bicycle factory. A film producer happened to catch sight of her one morning waiting at a bus stop, as he drove past in his big car. He told the driver to stop, and he got out to speak to the girl. He asked her if she would like to go to the film studio to do a test, and at first she thought he was joking. Then she got angry and said she would call the police. It took the producer twenty minutes to tell Connie that he was serious. Then an appointment was made for her to go to the studio the next day. The test was successful. They gave her some necessary lessons and within a few weeks she was playing the leading part opposite one of the most famous actors of the day. Of course, she was given a more dramatic name, which is now world-famous. But chances like this happen once in a blue moon!

An assistant stage manager’’s job is difficult because he has to________.

A．do all kinds of stage work

B．work for long hours

C．wait for a better company

D．act well

电测法是如何进行温度补偿？

点H坐标为（4，-3），把点H向左平移5个单位到点H'，则点H′的坐标为（    ）。

补全句子。

1. My __________ is Li Ming. (我的名字叫李明。)   

2. __________, My name is Danny. (你好，我的名字叫丹尼。)   

3. Hi, My name is __________. (你好，我的名字叫珍妮。)

在下列几种物态变化现象中，属于升华的是_______；属于凝华的是_______；其中②③⑤是_______（填“放热”或“吸热”）过程．  

①晾在室外的湿衣服变干了  

②夏天，揭开冰棒包装纸后会看到冰棒冒“白气”  

③冬天，河面上结了一层冰  

④放在衣柜里的樟脑丸会越来越小，最后“消失”了  

⑤严冬的深夜，教室窗玻璃的内表面上有一层冰花  

⑥铺柏油马路时，将沥青块放在铁锅中加热