A server has two PCI-X buses with four Active PCI-X slots.  Slots 1 and 2 are on the first PCI-X bus （100MHz） and slots 3 and 4 are on the second PCI-X bus （133MHz）. The customer requires you to install adapter A and adapter B on day one.  After the server has been installed and configured， the server must  be running 24 by 7 with no downtime. Three months later， adapter C needs to be hot added. All the adapters are 64-bit and capable of speeds up to 133MHz.  The customer’s priority is to have no downtime， and performance is secondary.  
Based on the information provided， into which slots should adapters A and B be installed in and later into which slot would adapter C be hot-added？（）

A.Adapter A in slot 1， adapter B in slot 4 and hot-add adapter C in slot 3
B.Adapter A in slot 1， adapter B in slot 3 and hot-add adapter C in slot 2
C.Adapter A in slot 2， adapter B in slot 4 and hot-add adapter C in slot 3
D.Adapter A in slot 3， adapter B in slot 1 and hot-add adapter C in slot 4