"All work and no play make Jack a dull boy."is a popular saying in the USA. It is true that aii of us n-  1   recreation (娱乐). We can't work all time if we want to keep h   2    and enjoy life.

     Everyone h  3   his own way of relaxing. Perhaps taking part in sports is the most p   4   way of all. There are team s   5   such as basketball and football. There are individual(个人的) sports such as swimming and r  6  . Skating and mountain c  7   are the most popular sports for people who like to be outdoors.

     Not everyone who enjoys sports likes to take part in them. Many people like w   8   TV or listening to music on the radio. So many people like some indoor recreations such as watching TV, singing and dancing. It doesn't matter whether we like indoor recreations or take part in outdoor sports. It is i  9   for everyone to relax after a day's work or study, and enjoy t  10   .

褶皱构造的基本形式有哪两种，分别简述其特征。