16．(1)                                  

(2)                                  

             图6               图7                      图8

  15． (1)                  (2)                     (3)

  14．                                                                   

  13．                                                                   

  12．                                                                   

  11．                                                                   

  10．                                                                   

  9．                                                                    

  8．(1)                     (2)                        (3)