读我国大陆东部季风区四地日平均气温≥10℃的开始日期与结束日期示意图，回答题。                                                                                                                                                                                                                                                                                                                                                                                                    

小题1:若只考虑纬度因素，则四地纬度由高到低排列正确的是

A．①②③④

B．①③②④

C．④②③①

D．④②①③小题2:当③地的纬度较④地低，则③地可能是

A．东南丘陵

B．华北平原

C．四川盆地

D．青藏高原

何为极冰的正反馈作用？