过滤操作中的要点常简记为“一贴二低三靠”,请你解释其具体含义：

①“一贴”：____________________________________________________________

②“二低”：________________________________________________________       ，

                                                                                                                            ；

③“三靠”：___________________________                                                          ， 

                                                                                                                            ，

                                                                                                                            。