避雷线比导线多出的那个控制应力是指（）。

     For several years, Americans have enjoyed teleshopping-watching TV and buying things by phone. Now
teleshopping is  1  in Europe. In a number of European countries, people  2  rurn on their TVs and shop for
clothes,jewelry, food, and many other things.
    Teleshopping is becoming  3  in Europe. The biggest Swedish company sells different kinds of things on
TV in European countries,and in one year it can  4  about $100 million. In France there are two teleshopping 
 5 , and the French spend about $20 million a year buying things  6  these channels. In Germany, teleshopping
was only one channel for an hour every day last year. Now the government  7  opening other channels for
teleshopping,including the largest American teleshopping company and a 24-hour teleshopping company.
German businessmen hope this new teleshopping will help them sell  8  things.
     Some people like teleshopping  9  they can do some shopping without leaving their homes, espccially in
the  10  with heavy traffic.  11  at the same time,other Europeans do not like this new way of shopping. They
call teleshopping "Junk  12 ".They usually  13  the quality of the things sold on TV.
     The  14  for high quality makes the European teleshopping companies have to be different from the
American companies.  15  will have to be more careful about the quality of the things they sell if they want
to make money.