What does SAP SuccessFactors recommend to create new and custom associations between Foundation Objects?

What does SAP SuccessFactors recommend to create new and custom associations between Foundation Objects?
A . All new and custom associations should be built between an MDF FO and another MDF FO
B . All new and custom associations should be built as One to Many
C . All new and custom associations should be built between an XML FO and another XML FO
D . All new and custom associations should be built as One to One

Answer: B