Explanation
The account category reference is a grouping of material types that have a similar account determination. By assigning the same account category reference to different material types, you can control that they use the same valuation class for account determination. The valuation class is a key factor that determines which general ledger accounts are posted during inventory transactions. Therefore, if you want to set up the same account determination for raw materials (material type ROH) and operating supplies (material type HIBE), you can group them by assigning the same account category reference to these material types.References:
[SAP Help Portal], [SAP Help Portal]

Explanation
The stock determination strategy is a set of rules that defines how the system selects a suitable stock for a material requirement. To use a stock determination strategy for a material in management, some prerequisites are needed. First, a stock determination rule must be assigned to the business transaction in Customizing. This rule specifies which stock types and special stocks are allowed for the transaction. Second, a stock determination rule must be customized and assigned to the storage type. This rule defines the sequence in which the system searches for available stock within the storage type. Third, a cross-application strategy for stock determination must be customized. This strategy determines how the system selects a storage location and a batch for the material requirement. The other options are not prerequisites, as they are optional or not related to the stock determination strategy.References: [SAP Help Portal], [SAP Community]