Consider a $\frac{208}{120}V,3-$phase, wye$-$connected, $4-$wire transformer. Each $120-$V phase feeds a separate and identical dc power supply comprising a simple full$-$wave bridge rectifier followed by a large filter capacitor. There are a total of three dc power supplies, one connected to each phase. The following circuit diagram shows one of the three power supplies:

The outputs of the three power supplies are loaded with identical resistive loads. There are no other loads on the transformer. Which of the following oscilloscope traces of the neutral current

B$.$

C$.$

D$.$ The trace is essentially flat.