I agree that A is the right answer since MDM is the master for Customers and Prospects MDM must be integrated with Sales Cloud which eliminates B and D. C is not the answer as Invoices have to be integrated into Salesforce for Display. Sales consultants should access inventory but it is not related to Salesforce, they can get that access through inventory system directly.

I believe C is the right one.
reasons:
1. Invoice system is drawn is a different shape (it looks to be an ERP module) so no need to specify it in the landscape.
2. MDM is clearly a must have.
3. Sales users need to access to the BI Tool, so BI and DW should be there.

They need access to inventory and B is the only answer that contains inventory.

I vote for B as it is the only to have Inventory

A is the right answer.

A is right answer
Since "Quotes should be generated in Salesforce with pricing from ERP." no need for SF to be integrated with Pricing Engine.
MDM is the master => integration required
Invoices should be accessible in Salesforce. => integration required