The New Year party is ________ the evening of January 1st.
A:of
B:in
C:on
D:at
定义域R的奇函数f(x),当x∈(﹣∞,0)时f(x)+xf′(x)<0恒成立,若a=3f(3),b=f(1),c=﹣2f(﹣2),则( )