For 16-QAM, the statement that _____________________ is correct.
A、the noise performance of 16-QAM is better than 16-PSK
B、the noise performance of 16-QAM is worse than 16-PSK
C、the noise performance of 16-QAM is better than QPSK
D、the noise performance of 16-QAM is worse than QPSK