CCNA R&S Deluxe Study Guide - Chapter #15 - Review Question #2 Pg. 643
The question is not clear and gives vague information. The answer in Appendix B shows very concise information that there would have been no way for a student to have known this information.
"2. You have configured your switches with the spanning-tree vlan x root primary and spanning-tree vlan x root secondary commands. Which of the following tertiary switch will take over if both switches fail?"
"2. D. Option A seems like the best answer, and had switches not been configured with the
primary and secondary command, then the switch configured with priority 4096 would
have been root. However, since the primary and secondary both had a priority of 16384,
then the tertiary switch would be a switch with a higher priority in this case."
Thank you for your report, Gabriel--we'll get it to the editorial department for review.
Tom with Wiley