NG-SDH equipment allocates ECC channel numbers according to certain principles. For example, by default, a four-optical port board is first inserted in slot 4 and the board is assigned channel numbers 0, 1, 2, 3, and then an SL16 board is inserted in slot 2. The assigned channel number is 4, if at this time unplug 2 No. slot SL16 plate, inserted a four-optical-port board in No. 8 slot, what is the assigned channel number?
A . 5 ， 6 ， 7 ， 8
B . 4 ， 5 ， 6 ， 7
C . 4 ， 6 ， 7 ， 8
D . Random allocation
Answer: B