Regarding the test item of IEEE 1588V2 time protection function, which of the following statements is wrong?

Regarding the test item of IEEE 1588V2 time protection function, which of the following statements is wrong?
A . On the OptiX OSN 8800, the active and standby states of the clock board and the cross board are related to each other. When performing a switch test, it is recommended to switch only the cross board or clock board.
B . On the OptiX OSN 6800, the active and standby states of the clock board and the cross board are related to each other. When performing a switch test, it is recommended to switch only the cross board or clock board.
C . Testing the long-term stability of time performance in PTP synchronization mode, the time performance of the output should be within ± 1us.
D . Long-term jitter test in physical layer synchronization mode, using a time analyzer with a GPS receiver to observe at the last node for more than 8 hours, the test output time performance should be within ± 1us.

Answer: B