已知：A={'Q':10} B={'Q':15}N={}能使n={'Q':25}的代码是（）

A、N'Q']=a.get('Q')+b.get('Q')
B、N'Q']=n.get('Q')+a.get('Q')+b.get('Q')
C、N'Q']=n.get('Q',0)+a.get('Q')+b.get('Q')
D、N'Q']=n.get('Q',0)+a.get('Q')N'Q']=n.get('Q',0)+b.get('Q')