【单选题】

+2.00DC×90°与-2.00DC×l80°联合后得到( )
A．+2.00DS/-2.00DC×90°

B．+2.00DS/-4.00DC×180°
C．+2.00DS/-4.00DC×90°
D．-2.00DS/+2.00DC×90°
E．-2.00DS/+4.00DC×180°