Which one is the bandwidth for a signal transmitting at 12 Mbps for QPSK (d=0)?

Which one is the bandwidth for a signal transmitting at 12 Mbps for QPSK (d=0)?

a) 2 MHz
b) 4 MHz
c) 6 MHz
d) None of the above

From the Combined Bank Assistant Engineer (IT) 2020 – Preliminary exam, question 11 of 37.

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