A:CH3CH═CH-CH2CH2CH3
B:CH2═CH(CH2)3CH3
C:CH3CH2CH═CHCH═CHCH2CH3
D:CH3CH2CH═CHCH2CH3
—No, Mom. I did it very carefully.
已知函数f(x)=x2+4x,x≥04x-x2,x<0,若f(2-a2)>f(a),则实数a的取值范围是( )