A.Group1-Slots 0 1 Group 2 – Slot 2 Group 3- Slot 3 Group 4 – Slot 4
B.Group1-Slots 2 3Group 2- Slot 4 Group 3-Slot 5 Group 4 – Slot 6
C.Group1-Slot 2 Group 2- Slot 3 Group 3 – Slot 4 Group 4 – Slot 5 6
D.Group1-Slot 3 Group 2 – Slot 4 Group 3 -Slot 5 Group 4 – Slots 6 7
参考答案：B
