— How was your trip in Chengdu?

— Not so good. I stayed there for two days. But it rained on _____ of the days.

                                                                                                                                                        [ ]

A. none          

B. neither      

C. both        

D. all

根据《国家突发环境事件应急预案》，将突发环境事件的预警分为四级，预警级别由低到高，颜色依次为（）。根据事态的发展情况和采取措施的效果，预警颜色可以升级、降级或解除。