阅读理解。 I don't know how it is that when I go to a post office I always seem to find myself in a line behind someone who has some long and complicated business to do. Having only come in to buy a couple of stamps, I am obliged to wait patiently while an old lady takes ten minutes to complete a form that a child could do in one. People in other lines move quickly forward to take their turns and are served by cheerful clerks. Sometimes, feeling that I cannot bear waiting in my motionless line any longer, I decide to join another one. It may be longer, but at least it is moving. This always turns out to be the worst thing I could have done. Not only have I now lost my place in the first line but the one I am in now slows to a stop. An angry argument suddenly develops between the clerk and the customer at the counter, or information is asked for which results in the clerk having to ask a senior official or, if it's a particularly difficult problem, disappear into a back room. Why it takes him so long, I don't know. Perhaps he has a quick snack, but, no, that can't be right because when at last my turn comes, he pushes forward a printed sign, saying ' Position Closed' and without a smile says, 'Sorry, going to lunch' 1. When the writer goes to the post office  _____. A.  he always has a lot of business to do B. he always has to fill in a form C. he only buys stamps D. he has to try to be patient 2. Why does the writer sometimes decide to join a line at another counter? A. There aren't so many people waiting there. B. The clerk is more cheerful. C. The people are moving. D. The clerk is not so busy. 3. What usually happens after the writer has joined another line? A. It gradually stops B. It stops suddenly C.  It keeps stopping D. It doesn't stop 4. Why does the writer think the clerk goes into a back room? A. To have his lunch B. To get some information C. To have a rest D. To talk to someone 5. What happened when it is the writer's turn to be served? A. The clerk tells him to go away B. The clerk goes off duty C. The clerk gives him a sign D. The clerk offers him a position