Which of the following is not an advantage of the enhanced MSTP built-in PCM solution over the traditional solution?

Which of the following is not an advantage of the enhanced MSTP built-in PCM solution over the traditional solution?
A . Reduce the number of network failure points and improve network reliability
B . Save room space
C . End-to-end management services, simple operation and maintenance
D . Improve signal transmission quality

Answer: D