单项选择题

理想运放电路如图所示,若R 1 =5kΩ,R 2 =20kΩ,R 3 =10kΩ,R 4 =50kΩ,u 1 -u 2 =0.2V,则u 0 为______

A.-4V
B.-5V
C.-8V
D.-10V