扦插时往往要对适宜扦插的材料进行一定的处理，才能使其更易成活。请你以月季为例，设计一实验方案，探究月季茎段下方的切口，怎样处理。
才更易成活。
（1）你提出的问题是                            ；
（2）你做出的假设是                            ；
（3）方案：a：                                                                                                              
b：                                                                                                                
c：                                                                                                          
（4）结论：                                                      。