In the series-inverter control method
(a) two inverters are connected back-to-back
(b) the output from the inverter is taken serially
(c) output voltages of two inverters are summed up with the help of a transformer
(d) output voltages of two inverters are summed up with the help of a third inverter
I have been asked this question during a job interview.
Question is from Voltage Control in Inverters in section Inverters of Power Electronics