命题“a=0，则ab=0”的逆否命题是（　　）

熟悉（shú  shóu）____    叮嘱（zhǔ shǔ）____      审视（shěn  sěng）____

严肃（sù   shù）____     半晌（shǎng xiǎng）____   嘲笑 （cháo cáo）____

       The umbrella is a very common object. It keeps the1   and the sun off the people. Most umbrellas can be folded up(折叠) so it is  2 to carry them.

     However, the umbrella has not always been as   3  as it is now. In the past, it was a symbol of importance. Some African countries still use umbrellas in this   4. Someone carries an umbrella and walks behind the king or important person.

     Umbrellas are very old. People in different parts of the world began to   5  umbrellas at different times. The Chinese had them more than 3,000 years ago. From there , umbrellas 6   to India and Egypt. In Greece and Rome,  7 wouldn't use them. They believed umbrellas were only for women.

     England was  8   the first country in Europe where common people used umbrellas against rain. The weather there is very  9  and umbrellas are very useful.

     Everybody uses umbrellas today. The next time you  10   one, thinking that for centuries only great men and women used them, you'll feel you are important people, too.

6＋8=____