Which statement is correct about Rapid Spanning Tree Protocol?

A. RSTP allows for multiple root bridges.
B. RSTP is backward compatible with STP.
C. RSTP has a convergence time of around 50 seconds.
D. RSTP has five port states to which the interfaces could possibly transition.

B. RSTP has three transition modes and converges faster than STP, which is 50 seconds. It is, however, backward compatible with STP 802.1d.