Which of the following descriptions about the Optix OSN 9800 subrack are correct?

When the OSN 9800 P18 is used as the slave subrack, the IU18 slot can only be inserted into the service board

When the OSN 9800 universal platform subrack is used as the slave subrack, the main control board must be placed

In the OSN 9800 U32 subrack, IU70 is the active CTU and IU78 is the standby CTU

The OSN 9800 U16 subrack has a total of 16 service slots, these slots have the same capacity, and the maximum support single slot 400bit/s ODUK crossover